Production method of microlens array, liquid crystal display device and production method thereof, and projector

ABSTRACT

A method of producing a microlens array includes a patterning step of forming a first optical resin layer having a first refractive index on a transparent substrate and forming a plurality of microlens planes arrayed in a two-dimensional pattern on the front surface of the first optical resin layer; a planarizing step of forming a planarized second optical resin layer; a joining step of providing a support layer on which a transparent protective film is previously formed; and a removing step of removing the support layer in such a manner that only the protective film remains on the second optical resin layer. The planarizing step is performed by filling irregularities of the microlens planes with a resin having a second refractive index and planarizing the front surface, opposed to the microlens planes, of the resin, to form the planarized second optical resin layer, and the joining step is performed by joining the support layer to the planarized second optical resin layer. With this method, a microlens array excellent in surface accuracy and flatness can be produced without the need of provision of a support layer made from glass.

The subject matter of application Ser. No. 10/436,020 is incorporatedherein by reference. The present application is a continuation of U.S.application Ser. No. 10/436,020, filed May 12, 2003 now U.S. Pat. No.6,894,840, which claims priority to Japanese Patent ApplicationNoJP2002-137709, filed May 13, 2002, and Japanese Patent Application No.JP2002-168013, filed Jun. 10, 2002. The present application claimspriority to these previously filed applications.

BACKGROUND OF THE INVENTION

The present invention relates to a method of producing a microlensarray, a liquid crystal display device incorporating the microlens arrayand a method of producing the liquid crystal display device, and aprojector using the liquid crystal display device as a light bulb.

Projectors using an LCD (Liquid Crystal Display Device), DMD (DigitalMirror Device), or LCOS (LC•ON•SILICON) as a light bulb has beenactively developed. From the viewpoints of function and shape,projectors are classified into a data projector mainly used for monitordisplay for personal computers, a front projector or a rear projectormainly used for AV for home theaters and the like, and a rear projectorfor TV. Meanwhile, from the viewpoint of the number of light bulbs,projectors are classified into a one-screen type, a two-screen type, anda three-screen type. The light bulbs are classified into a transmissiontype and a reflection type.

The higher luminance characteristics of projectors may be required inthe future. To meet such a requirement it is primarily expected toimprove optics. For example, it is expected to enhance the luminance ofa light source to be used, to shorten the arc length (for realizingpointed light source) in the case of using an arc lamp, to optimizeoptical members, and to miniaturize optical members.

To meet the above requirement, it is secondarily expected to increasethe aperture ratio of a light bulb as a key device of a projector. Inthis case, it is basically required to realize a finer structure and ahigher aperture ratio of the device at the pixel level. If liquidcrystal is used as an electro-optical medium, however, the apertureratio of pixels cannot be enhanced only by providing a simple finestructure of the device. The reason for this is as follows: namely,since liquid crystal is a continuous body, a shielding black matrixhaving an area being large enough to prevent leakage of light fromreverse tilt domains and to prevent leakage of light of thin filmtransistors for driving the liquid crystal must be provided, with aresult that the aperture ratio of pixels are correspondingly sacrificed.

To improve the utilization efficiency of light emitted from a lightsource and also to enhance the luminance, an attempt has been made tomount microlens arrays to liquid crystal display devices. For example, aflat display device incorporating a microlens array has been disclosedin Japanese Patent Laid-open No. Hei 2000-206894. A microlens arrayincorporated in a high precision liquid crystal display device (liquidcrystal panel) for a related art liquid crystal projector has beenproduced by using a glass substrate such as a quartz substrate or aneoceram glass substrate (hereinafter, the glass substrate used for amicrolens array is sometimes referred to as “cover glass”). To be morespecific, a method of forming a microlens array using the cover glass bya wet-etching or dry-etching process or a 2P (Photo-Polymerization)process has been put into practical use. In each case, a region in whicha microlens array is to be formed is composed of a transparent resin.The thickness of a cover glass for supporting such a transparent resinhas been reduced by polishing or grinding in a controlled manner, and atransparent conductive film (for example, ITO film) for a display devicehas been formed on the cover glass, as needed.

A related art method of producing a microlens array by using a wetetching process will be described with reference to FIGS. 1A to 1D.

In a step shown in FIG. 1A, after a quartz substrate is cleaned, aresist is applied on the quartz substrate, and is patterned into apattern corresponding to an array pattern of pixels by exposure anddevelopment. In a step shown in FIG. 1B, the quartz substrate issubjected to isotropic etching via the resist, to form spherical lensplanes R. In addition, a film of a metal, polysilicon, or amorphoussilicon excellent in chemical resistance may be used as a mask in placeof the resist. The etching may be performed by using an HF or BHF basedetchant.

In a step 1C, a cover glass is stuck on the surface of the quartzsubstrate, and a gap therebetween is filled with a transparent resinhaving a refractive index different from that of quartz by vacuuminjection, spin coating, or spraying. The resin in the spherical lensplanes formed by wet etching is perfectly cured by UV irradiation orheating. Examples of the resins used herein include an epoxy basedresin, an acrylic based resin, a silicon based resin, and a fluorinebased resin, each of which is curable by UV-irradiation or heating. Inthis way, microlenses arrayed in a pattern corresponding to an arraypattern of pixels are formed. Finally, in a step 1D, the cover glass ispolished, and a transparent electrode made from ITO is formed, to form acounter substrate. While not shown, the counter substrate is stuck on adrive substrate on which pixel electrodes and thin film transistors arepreviously formed, and liquid crystal is injected in a gap therebetween,to obtain an active matrix type liquid crystal display device.

FIG. 2 shows a schematic configuration of optics (mainly, illuminationoptics) of a related art projector. The projector includes a lightsource 1101, a first microlens array 1102, a second microlens array1103, a PS synthesizing element 1104, a condenser lens 1105, a fieldlens 1106, a liquid crystal panel 1107, and a projection lens 1108,which are arranged in this order along an optical axis 1100. Themicrolens array 1102 has a plurality of microlenses arrayed in atwo-dimensional pattern, and the microlens array 1103 has a plurality ofmicrolenses arrayed in a two-dimensional pattern. The PS synthesizingelement 1104 includes a plurality of half-wave plates 1104A at positionseach of which corresponds to a space between adjacent two of themicrolenses of the second microlens array 1103.

In this projector, illumination light emitted from the light source 1101passes through the microlense arrays 1102 and 1103, to be divided into aplurality of micro-beams. The light emerged from the microlens arrays1102 and 1103 is made incident on the PS synthesizing element 1104.Light L10 incident on the PS synthesizing element 1104 contains aP-polarized component and an S-polarized component perpendicular to eachother within a plane perpendicular to the optical axis 1100. The PSsynthesizing element 1104 separates the light L10 incident thereon intotwo kinds of polarized light components L11 and L12 (P-polarizedcomponent and S-polarized component). Of these polarized lightcomponents L11 and L12, the polarized light component L11 (for example,P-polarized component) emerges from the PS synthesizing element 1104with its polarization direction (for example, P-polarization) kept as itis, and the polarized light component L12 (for example, S-polarizedcomponent) is converted into the other polarized light component (forexample, P-polarized component) by the half-wave plates 1104A, and theconverted light component L12 emerges from the PS synthesizing element1104. As a result, the two separated polarized light components L11 andL12 are directed in a specific direction.

The light emerged from the PS synthesizing element 1104 passes throughthe condenser lens 1105 and the field lens 1106, and illuminates theliquid crystal panel 1107. The micro-beams divided from the light by themicrolens arrays 1102 and 1103 are enlarged at an enlargement ratiodetermined by the focal distance “fc” of the condenser lens 1105 and thefocal distance “f” of the microlenses 1103M of the second microlensarray 1103, to illuminate the entire incident plane of the liquidcrystal panel 1107. Accordingly, a plurality of the enlarged beams aresuperimposed on the incident plane of the liquid crystal panel 1107, torealize uniform illumination as a whole. The liquid crystal panel 1107spatially modulates the incident light on the basis of image signals,and the light emerged from the liquid crystal panel 1107 is projected ona screen (not shown) by the projection lens 1108, to form an image onthe screen.

FIG. 3 is a typical perspective view showing one example of a liquidcrystal panel. A liquid crystal panel (liquid crystal display device)shown in the figure has a flat panel structure including a pair ofsubstrates 1201 and 1202 and liquid crystal 1203 kept therebetween. Apixel array portion 1204 and a drive circuit portion are integrated onthe lower substrate 1201. The drive circuit portion is separated into avertical drive circuit 1205 and a horizontal drive circuit 1206.Terminals 1207 for external connection are formed on a peripheral upperend of the lower substrate 1201. The terminals 1207 are connected to thevertical drive circuit 1205 and the horizontal drive circuit 1206 viawiring lines 1208. Gate lines G and signal lines S are formed on thepixel array portion 1204. A pixel electrode 1209 and a thin filmtransistor (TFT) 1210 for driving the pixel electrode 1209 are formed ateach of intersections between the gate lines G and the signal lines S. Apixel P is composed of a combination of the pixel electrode 1209 and thethin film transistor 1210. A gate electrode of the thin film transistor1210 is connected to the corresponding gate line G, a drain resinthereof is connected to the corresponding pixel electrode 1209, and asource region thereof is connected to the corresponding signal line S.The gate line G is connected to the vertical drive circuit 1205, and thesignal line S is connected to the horizontal drive circuit 1206. Thevertical drive circuit 1205 sequentially selects each pixel P via thegate line G. The horizontal drive circuit 1206 writes an image signal onthe selected pixel P via the signal line S. The lower substrate 1201, onwhich the pixel electrodes and the thin film transistors (TFTs) areintegrated, is called as a TFT substrate. While not shown, a counterelectrode and color filter are formed on the upper substrate 1202, andtherefore, the upper substrate 1202 is called as a counter substrate.

Such a microlens array must meet the requirement toward higher precisionas well as the requirement toward higher luminance. For example, as thepanel size of a liquid crystal display device becomes small, the pixelsize becomes small in proportion thereto, and correspondingly, a coverglass must be made thin. Although a cover glass has been thinned bypolishing or grinding, such polishing or grinding has a limitation inthinning the cover glass at a desired accuracy, thereby making itdifficult to ensure the uniformity and flatness required for design. Ifthe accuracy and flatness of the plane of a cover glass for a microlensarray is insufficient, there arises a problem that mechanical stress mayoccur at the time of assembling the microlens array in a liquid crystaldisplay device. Also, in the case of thinning a cover glass to 30 μm orless along with the requirement toward higher definition of a panel,there arises another problem that waviness or warping of the cover glassmay occur by stress due to shrinkage caused by curing of an opticalresin forming the microlens array or a difference in thermal expansioncoefficient between the optical resin and the cover glass.

In the case of using the above-described active matrix type liquidcrystal display device as a light bulb of a projector, such a liquidcrystal display device is more strongly required for higher definitionand high luminance. From this viewpoint, a high temperature polysiliconthin film transistor capable of realizing high definition is used as aswitching device for driving each pixel. Along with the demand toward afiner switching device, a microlens array is required to have a finerstructure. To meet such a requirement, a technique of integrating amicrolens array to a substrate of an active matrix type liquid crystaldisplay device has been developed. For example, a method of producing amicrolens array incorporating substrate has been disclosed, for example,in Japanese Patent Laid open No. Hei 5-341283, Hei 10-161097, and2000-147500.

A duel microlens array structure is regarded as an ideal structurecapable of realizing the maximum luminance, wherein a microlens arrayfunctioning as condenser lenses is assembled in a counter substrate onthe light incident side, and a microlens array functioning as fieldlenses is assembled on a TFT substrate side. Such a duel microlens arrayis able to enhance the effective aperture ratio of pixels at maximum;however, because of the most difficulty in producing the duel microlensarray, any practical production method thereof has been not disclosed atpresent. It is to be noted that an LCD having a duel microlens arraystructure is often called as an MTMLCD abbreviated from “MicrolensSubstrate-TFT Substrate-Microlens Substrate LCD”.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a method ofproducing a microlens array excellent in surface accuracy and a flatnesswhile eliminating the need of provision of a cover glass (glasssubstrate), and to provide a method of producing a so-called duelmicrolens array (sometimes called as a double microlens array) in whichtwo microlens arrays are joined to each other by using a planarizingtechnique.

A second object of the present invention is to provide a liquid crystaldisplay device incorporating the above microlens array.

A third object of the present invention is to provide a projector usingthe above liquid crystal display device.

A fourth object of the present invention is to provide a method ofrationally producing a liquid crystal display device having a dualmicrolens array.

To achieve the above first object, according to a first aspect of thepresent invention, there is provided a method of producing a microlensarray, including a patterning step of forming a first optical resinlayer having a first refractive index on a transparent substrate andforming a plurality of microlens planes arrayed in a two-dimensionalpattern on the front surface of the first optical resin layer; aplanarizing step of forming a planarized second optical resin layer; ajoining step of providing a support layer on which a transparentprotective film is previously formed; and a removing step of removingthe support layer in such a manner that only the protective film remainson the second optical resin layer. In this method, the planarizing stepincludes a step of filling irregularities of the microlens planes with aresin having a second refractive index and planarizing the frontsurface, opposed to the microlens planes, of the resin, to form theplanarized second optical resin layer, and the joining step includes astep of joining the support layer to the planarized second optical resinlayer.

The joining step may be performed before the planarizing step. In thiscase, the joining step may include a step of joining the support layerto the microlens side of the first optical resin layer with a specificgap kept therebetween, and the planarizing step may include a step offilling the gap with a liquid resin and curing the resin, to form theplanarized second optical resin layer.

The planarizing step may include a step of coating the front surface ofthe first optical resin layer with a liquid resin by a spin-coatingprocess so as to fill the microlens planes with the liquid resin and toplanarize the front surface of the liquid resin, to form the polarizedsecond optical resin layer.

The planarizing step may include a step of supplying a resin on thefront surface side of the first optical resin layer to fill themicrolens planes with the resin, and pressing the front surface, opposedto the microlens planes, of the resin with a stamper having a flatplane, to form the planarized second optical resin layer.

The protective film is preferably made from SiO₂, SiN, a-DLN, or Al₂O₃.

To achieve the above first object, according to a second aspect of thepresent invention, there is provided a method of producing a microlensarray, including a patterning step of forming a first optical resinlayer having a first refractive index on a transparent substrate andforming a plurality of microlens planes arrayed in a two-dimensionalpattern on the front surface of the first optical resin layer; and afilling/plarizing step of filling irregularities of the microlens planeswith a resin having a second refractive index, and planarizing the frontsurface, opposed to the microlens planes, of the resin, to form a secondoptical resin layer. In this method, the filling/planarizing step isperformed by a spin-coating process.

To achieve the above first object, according to a third aspect of thepresent invention, there is provided a method of producing a microlensarray, including a patterning step of forming a first optical resinlayer having a first refractive index on a transparent substrate andforming a plurality of microlens planes arrayed in a two-dimensionalpattern on the front surface of the first optical resin layer; a fillingstep of filling irregularities of the microlens planes with a resinhaving a second-refractive index; and a planarizing step of planarizingthe front surface, opposed to the microlens planes, of the resin fillingthe microlens planes, to form a second optical resin layer. In thismethod, the planarizing step is performed by planarizing the frontsurface of the resin filling the microlens planes by a flat stampingprocess.

To achieve the above first object, according to a fourth aspect of thepresent invention, there is provided a method of producing a microlensarray having a double structure, including a first patterning step offorming a first optical resin layer on a first support and formingtwo-dimensionally arrayed first microlens planes on the front surface ofthe first optical resin layer; a first planarizing step of fillingirregularities of the first microlens planes with an optical resinhaving a refractive index different from that of the first optical resinlayer, and planarizing the front surface, opposed to the microlensplanes, of the optical resin, to form a first microlens array; a secondpatterning step of forming a second optical resin layer on a secondsupport and forming two-dimensionally arrayed second microlens planes onthe front surface of the second optical resin layer; a secondplanarizing step of filling irregularities of the second microlensplanes with an optical resin having a refractive index different fromthat of the second optical resin layer, to form a second microlensarray; and a joining step of joining the planarized surface of the firstmicrolens array to the planarized surface of the second microlens arrayin a state that the first microlens planes are aligned to the secondmicrolens planes, thereby integrating the first and second microlensarrays to each other.

To achieve the above second aspect, according to a fifth aspect of thepresent invention, there is provided a liquid crystal display devicehaving a panel structure including a drive substrate on which at leastpixel electrodes and switching devices for driving the pixel electrodesare formed; a counter substrate on which at least a counter electrode isformed; and a liquid crystal layer interposed between the drivesubstrate and the counter substrate joined such that the pixelelectrodes are opposed to the counter electrode with a specific gap kepttherebetween. In this device, a microlens array composed of microlensarrayed in a two-dimensional pattern corresponding to an array patternof the pixel electrodes is assembled at least to the counter substrate.The microlens array has the back surface joined to the counter substrateand the front surface planarized, and the counter electrode is formed onthe planarized front surface of the microlens array via a protectivefilm.

Preferably, after the protective film previously formed on a support isbonded on the planarized front surface of the microlens array, thesupport is removed to expose the protective film, and the counterelectrode is formed on the exposed protective film.

The protective film is preferably made from Al₂O₃, a-DLC, TiO₂, TiN, orSi.

Preferably, the microlens array has a double structure including firstmicrolenses functioning as condenser lenses disposed on the side apartfrom the liquid crystal layer and second microlenses substantiallyfunctioning as field lenses disposed on the side close to the liquidcrystal layer, and the distance between a principal point of each of thesecond microlenses and the liquid crystal layer is set to a value in arange of 10 μm or less.

It is to be noted that if the focal distance of the second microlenscorresponds to the distance between both the first and secondmicrolenses, the function of the second microlens becomes 100%, and inactual, if the difference between the focal distance of the secondmicrolens and the distance between both the first and second microlensesis within about 10%, the second microlens sufficiently functions as afield lens.

To achieve the above second object, according to a sixth aspect of thepresent invention, there is provided a liquid crystal display devicehaving a panel structure including a drive substrate on which at leastpixel electrodes and switching devices for driving the pixel electrodesare formed; a counter substrate on which at least a counter electrode isformed; and a liquid crystal layer interposed between the drivesubstrate and the counter substrate joined such that the pixelelectrodes are opposed to the counter electrode with a specific gap kepttherebetween; wherein a microlens array composed of microlens arrayed ina two-dimensional pattern corresponding to an array pattern of the pixelelectrodes is assembled at least to the drive substrate. In this device,the microlens array has a stacked structure of a first optical resinlayer having a first refractive index and a second optical resin layerhaving a second refractive index. The first optical resin layer hasmicrolens planes arrayed in a two-dimensional pattern and the secondoptical resin layer is formed to fill irregularities of the microlensplanes and has a planarized front surface opposed to the microlensplanes. The microlens array is assembled to the drive substrate in sucha manner that the planarized surface of the second optical resin layerof the microlens array is joined to the back surface of the drivesubstrate.

Preferably, the microlens array is formed by joining the first opticalresin layer to a support layer having a protective film previouslyformed thereon with a specific gap kept therebetween, filling the gapwith a liquid resin and curing the liquid resin to form the secondoptical resin layer, and removing the support layer to expose theprotective film. The exposed surface of the protective film is taken asthe planarized surface of the second optical resin layer.

Preferably, the microlens array is formed by filling the microlensplanes of the first optical resin layer with a resin, and pressing thefront surface, opposed to the microlens planes, of the resin with astamper having a flat plane, to planarize the front surface of thesecond optical resin layer.

The liquid crystal display device preferably further includes amicrolens array disposed on the counter substrate in such a manner as tobe aligned to the microlens array disposed on the drive substrate,wherein one of the microlens arrays functions as condenser lenses andthe other functions as field lenses.

Preferably, the drive substrate is thinned by polishing the back surfacethereof, and the planarized surface of the second optical resin layer ofthe microlens array is joined to the polished back surface of the drivesubstrate.

To achieve the above third object, according to a seventh aspect of thepresent invention, there is provided a projector including a lightsource for emitting light; a liquid crystal display device having afunction of optically modulating incident light; and a projection lensfor projecting light modulated by the liquid crystal display device. Theliquid crystal display device having a panel structure includes a drivesubstrate on which at least pixel electrodes and switching devices fordriving the pixel electrodes are formed; a counter substrate on which atleast a counter electrode is formed; and a liquid crystal layerinterposed between the drive substrate and the counter substrate joinedsuch that the pixel electrodes are opposed to the counter electrode witha specific gap kept therebetween. In this device, a microlens arraycomposed of microlens arrayed in a two-dimensional pattern correspondingto an array pattern of the pixel electrodes is assembled at least to thecounter substrate. The microlens array has the back surface joined tothe counter substrate and the front surface planarized, and the counterelectrode is formed on the planarized front surface of the microlensarray via a protective film.

To achieve the third aspect, according to an eighth aspect of thepresent invention, there is provided a projector including a lightsource for emitting light; a liquid crystal display device having afunction of optically modulating incident light; and a projection lensfor projecting light modulated by the liquid crystal display device. Theliquid crystal display device having a panel structure includes a drivesubstrate on which at least pixel electrodes and switching devices fordriving the pixel electrodes are formed; a counter substrate on which atleast a counter electrode is formed; and a liquid crystal layerinterposed between the drive substrate and the counter substrate joinedsuch that the pixel electrodes are opposed to the counter electrode witha specific gap kept therebetween. In the device, a microlens arraycomposed of microlens arrayed in a two-dimensional pattern correspondingto an array pattern of the pixel electrodes is assembled at least to thedrive substrate. The microlens array has a stacked structure of a firstoptical resin layer having a first refractive index and a second opticalresin layer having a second refractive index. The first optical resinlayer has microlens planes arrayed in a two-dimensional pattern, and thesecond optical resin layer is formed to fill irregularities of themicrolens planes and has a planarized front surface opposed to themicrolens planes. The microlens array is assembled to the drivesubstrate in such a manner that the planarized surface of the secondoptical resin layer of the microlens array is joined to the back surfaceof the drive substrate.

To achieve the above object, according to a ninth aspect of the presentinvention, there is provided a method of producing a liquid crystaldisplay device having a panel structure including a first substratehaving the front surface on which at least pixel electrodes andswitching devices for driving the pixel electrodes are formed and theback surface opposed to the front surface; a second substrate having thefront surface on which at least a counter electrode is formed and theback surface opposed to the front surface; and a liquid crystal layerinterposed between the first and second substrates joined such that thepixel electrodes are opposed to the counter electrode with a specificgap kept therebetween. A first microlens array composed oftwo-dimensionally arrayed microlenses for individually condensing lightto the pixel electrodes is integrally formed on one of the first andsecond substrates. A second microlens array composed oftwo-dimensionally arrayed microlenses for allowing light individuallycondensed to the pixel electrodes to pass therethrough is integrallyformed on the other of the first and second substrates. The methodincludes a bonding step of bonding a base plate to the front surface ofeach of the first and second substrates; a polishing step of polishingthe back surface of the substrate in a state that the substrate is heldby the base plate, to reduce the thickness of the substrate; a stickingstep of sticking the corresponding one of the first and second microlensarrays to the polished back surface of the substrate via a transparentoptical resin having a refractive index higher or lower than that of thesubstrate; and a peeling step of peeling the base plate from the frontsurface of the substrate and cleaning the substrate, thereby integratingthe corresponding microlens array to the back surface of the substrate.

The method may further includes a dividing step of dividing, if at leastone of the first and second substrates is a multi-chip module substratehaving an area corresponding to a plurality of panels, the multi-chipmodule into single substrates corresponding to individual panels. Inthis case, after a plurality of the corresponding ones of the first andsecond microlens arrays, which correspond to the plurality of panels,are integrated to the multi-chip module substrate by the bonding step,polishing step, sticking step, and peeling step, the multi-chip modulesubstrate may be divided into single substrates corresponding toindividual panels at a suitable stage.

In the case where one of the first and second substrates is a multi-chipmodule substrate having an area corresponding to a plurality of panelsand the other is a single-chip module substrate, preferably, a pluralityof the corresponding ones of the first and second microlens arrays,which correspond to the plurality of panels, are formed on themulti-chip module substrate; the multi-chip module substrate isimmediately divided into single substrates corresponding to individualpanels in the dividing step; the single-chip module substrates to eachof which the corresponding one of the first and second microlens arraysis previously integrated are prepared; and the single substrates dividedfrom the multi-chip module substrate are overlapped to the single-chipmodule substrates in one-to-one relationship with a specific gap kepttherebetween, to be assembled into individual panels.

In the case where one of the first and second substrates is a multi-chipmodule substrate having an area corresponding to a plurality of panelsand the other is a single-chip module substrate, preferably, a pluralityof the corresponding ones of the first and second microlens arrays,which correspond to the plurality of panels, are formed on themulti-chip module substrate; the single-chip module substrates to eachof which the corresponding one of the first and second microlens arraysis previously integrated are prepared; the single-chip module substratesare assembled to the multi-chip module substrate; and the multi-chipmodule substrate assembled with the single-chip module substrates isdivided into individual panels in the dividing step.

In the case where one of the first and second substrates is a multi-chipmodule substrate to which a plurality of the corresponding ones of thefirst and second microlens arrays for a plurality of panels areintegrated, and the other of the first and second substrates is also amulti-chip module substrate to which a plurality of the others of thefirst and second microlens arrays for a plurality of panels areintegrated, preferably, the multi-chip module substrates are overlappedto each other with a specific gap kept therebetween, to be assembledinto a panel base corresponding to the plurality of panels; and thepanel base is divided into individual panels in the dividing step.

The dividing step may include a first dicing step of partially cuttingthe multi-chip module substrate along boundaries defined to partitionthe multi-chip module substrate into individual panels by first dicing,to form grooves having V-shapes in cross-section; and a second dicingstep of perfectly cutting the grooves by second dicing, thereby formingsingle substrates with chamfered end faces.

The method may include an alignment step of forming, after peeling thebase plate from the front surface of the substrate and cleaning thesubstrate in the peeling step, an alignment layer for aligning theliquid crystal layer on the exposed front surface of the substrate insuch a temperature range as not to impair the heat resistance of themicrolens array integrated to the substrate.

The method may include an alignment step of forming an alignment layerfor aligning the liquid crystal layer on the front surface of thesubstrate; wherein the alignment step is performed before the microlensarray is integrated to the back surface of the substrate by the bondingstep, polishing step, sticking step, and peeling step.

The polishing step may be performed by one or a combination of two ormore of buffing with a grade suitable for optics, particle blasting,chemical-mechanical polishing, and chemical etching.

In the polishing step, preferably, the thickness of the substrate isreduced by polishing the back surface of the substrate in such a mannerthat the focal point of each of microlenses of the second microlensarray functioning as field lenses corresponds to a principal point ofeach of microlens of the first microlens array functioning as condenserlenses at the time of assembling the first and second substrates into apanel.

The sticking step may include a step of preparing the microlens arraycomposed of microlens planes arrayed in a two-dimensional pattern byprocessing an optical glass material having a relatively low refractiveindex; and a step of positioning the microlens array to the polishedback surface of the substrate, overlapping the microlens array theretowith a specific gap kept therebetween, filling the gap with atransparent optical resin having a refractive index higher or lower thanthat of the substrate, and curing the transparent optical resin.

The sticking step may include a step of fixing the polished back surfaceof the substrate to the microlens array with a specific gap kepttherebetween by a seal material, filling the gap with a transparentoptical resin having a refractive index higher or lower than that of thesubstrate, and sealing the gap.

The microlens planes are preferably formed into spheric, aspheric, orFresnel shapes.

The method may further includes a cleaning step of cleaning the baseplate peeled as a spent product in the peeling step in order to re-usethe base plate.

The method may further include a preliminary step of integrating thecorresponding one of the first and second microlens arrays to the secondsubstrate; and an assembling step of assembling the second substrateintegrated with the microlens array to the front surface of the firstsubstrate. In this case, the bonding step may include a step of bondingthe base plate to the front surface side of the second substrateassembled on the front surface of the first substrate; the polishingstep may include a step of polishing the back surface of the firstsubstrate in a state that the panel is held by the base plate; and thesticking step may include a step of sticking the corresponding one ofthe first and second microlens arrays to the polished back surface ofthe first substrate.

The polishing step may include a step of polishing the back surface ofthe first substrate in a state that a plurality of terminals forexternal connection formed on the first substrate are kept at the samepotential.

The bonding step may include a step of mounting the second substrateside of the panel to the base plate fixed to a polishing platen used forthe polishing step.

According to the present invention, since the surface of a microlensarray is planarized by etching, flat stamping, or spin-coating, it ispossible to eliminate the need of provision of a glass substrate (coverglass). This is advantageous in thinning the microlens array, and inremoving mechanical stress at the time of assembling the microlens arrayto a liquid crystal display device. Further, since two microlens arrayscan be accurately joined to each other by making use of a planarizingtechnique such as etching, flat stamping, or spin-coating, it ispossible to stably produce a so-called dual microlens array.

According to the present invention, a microlens array incorporating TFTsubstrate is prepared by sticking a base plate on the front surface of aTFT substrate with an adhesive, polishing the back surface of the TFTsubstrate by a method for one-surface polishing with a grade suitablefor optics, to form a TFT thin substrate having a specific thickness,and sticking a microlens array on the TFT thin substrate with atransparent resin adhesive having a high refractive index. A microlensarray incorporating counter substrate is also prepared by a processsimilar to that described above. These substrates are overlapped to eachother with a specific gap kept therebetween, and liquid crystal isenclosed in a gap therebetween and is sealed, to produce a liquidcrystal display device having a duel microlens array structure. Such adual microlens type liquid crystal display device is suitable, forexample, for a light bulb of a projector. Since the microlens arrayfunctioning as condenser lenses for a liquid crystal layer and the othermicrolens array functioning as field lenses can be disposed inclose-proximity to each other, it is possible to obtain an optimalfunction of the microlenses, and hence to significantly improve theeffective aperture ratio of pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and advantages of the presentinvention will be more apparent from the following description inconjunction with the accompanying drawings, wherein:

FIGS. 1A to 1D are process diagrams showing a related art method ofproducing a liquid crystal display device;

FIG. 2 is a typical diagram showing one example of a related artprojector;

FIG. 3 is a typical perspective view showing one example of a liquidcrystal display device to be assembled in the projector shown in FIG.39;

FIGS. 4A to 4D are process diagrams showing a method of producing amicrolens array according to the present invention;

FIGS. 5A to 5C′ are process diagrams showing another method of producinga microlens array according to the present invention;

FIGS. 6A to 6D are process diagrams showing essential steps of a furthermethod of producing a microlens array according to the presentinvention;

FIG. 7 is a typical sectional view showing a reference example of a duelmicrolens array;

FIG. 8 is a graph showing optical characteristic of the microlens arrayshown in FIG. 7;

FIGS. 9A to 9E are process diagrams for illustrating a liquid crystaldisplay device according to the present invention;

FIGS. 10A to 10E are process diagrams for illustrating another liquidcrystal display device according to the present invention;

FIGS. 11A to 11E are process diagrams for illustrating a further liquidcrystal display device according to the present invention;

FIG. 12 is a typical partial sectional view showing a reference exampleof a general liquid crystal display device;

FIGS. 13A to 13F are process diagrams for illustrating a further liquidcrystal display device according to the present invention;

FIGS. 14A and 14B are enlarged views of the liquid crystal displaydevice shown in FIGS. 13A to 13F;

FIGS. 15A to 15F are process diagrams for illustrating a further liquidcrystal display device according to the present invention;

FIG. 16 is a typical diagram showing optical characteristics of a liquidcrystal display device according to the present invention;

FIG. 17 is a perspective view showing the entire configuration of aliquid crystal display device according to the present invention;

FIG. 18 is a typical diagram showing one example of a projectoraccording to the present invention;

FIGS. 19A to 19E are process diagrams showing a method of a liquidcrystal display device according to the present invention;

FIG. 20 is a process diagram showing an embodiment of the method ofproducing a liquid crystal display device according to the presentinvention;

FIGS. 21A and 21B are typical diagrams showing a dividing step of theproduction method;

FIG. 22 is a process diagram showing another embodiment of the method ofproducing a liquid crystal display device according to the presentinvention;

FIG. 23 is a typical diagram showing an assembling step of theproduction method;

FIGS. 24A and 24B are typical diagrams showing a method of producing amicrolens array incorporating counter substrate;

FIG. 25 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 26 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 27 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 28 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 29 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 30 is a process diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 31 is a typical diagram showing a further embodiment of the methodof producing a liquid crystal display device according to the presentinvention;

FIG. 32 is a typical diagram showing a panel taking a measure againststatic electricity;

FIG. 33 is a typical diagram showing another panel taking a measureagainst static electricity;

FIG. 34 is a typical diagram showing a polishing step;

FIG. 35 is a typical diagram showing another polishing step;

FIG. 36 is a sectional view showing a sticking step using an opticalresin;

FIG. 37 is a plane view of FIG. 36, showing the sticking step using anoptical resin;

FIGS. 38A to 38C are typical sectional views showing another polishingstep;

FIG. 39 is a sectional view showing one example of the liquid crystaldisplay device produced according to the present invention; and

FIG. 40 is a typical diagram showing one example of the liquid crystaldisplay device produced according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method of producing a microlens array, a liquid crystaldisplay device using the microlens array, a projector using the liquidcrystal display device, and a method of producing a liquid crystaldisplay device according to the present invention will be described inthis order with reference to the drawings, in which preferredembodiments are shown.

1. Method of Producing Microlens Array

A first embodiment of a method of producing a microlens array accordingto the present invention will be described with reference to FIGS. 4A to4D.

In a patterning step shown in FIG. 4A, a first optical resin layer 2having a first refractive index is formed on a substrate 1 made from atransparent glass or the like, and a plurality of microlens planesarranged in a two-dimensional pattern are formed on the surface of thefirst optical resin layer 2. In this embodiment, the first optical resinlayer 2 made from a UV-cured type resin having a low refractive index ispreviously formed on the glass substrate 1, and an Ni-electroformedoriginal having a plurality of microlens planes is stamped on thesurface of the first optical resin layer 2, to transfer the microlensplanes to the surface of the first optical resin layer 2. The firstoptical resin layer 2 made from the UV-cured type resin is cured byirradiating the first optical resin layer 2 with ultraviolet rays fromthe back side of the glass substrate 1, to fix the microlens planestransferred to the first optical resin layer 2.

In a joining step shown in FIG. 4B, a support layer 4 on which atransparent protective film 3 is previously formed is joined to theglass substrate 1 side by a seal material 5. The support layer 4 is madefrom a cover glass. The protective film 3 previously formed on onesurface of the support layer 4 functions as a polishing stopper at thetime of polishing the support layer 4 made from the cover glass in thesubsequent step. The protective film 3 may be made from an insulatingmaterial such as SiO₂, SiN, a-DLC (amorphous diamond-like carbon), orAl₂O₃. The seal material 5 for joining the support layer 4 to the glasssubstrate 1 side is composed of a resin applied along the outerperipheral portion of the support layer 4, and contains glass fibershaving diameters ranging from 2 to 3 μm as a spacer. The support layer4, the outer peripheral portion of which is coated with the sealer 5, isbonded on the glass substrate 1 side, to form an internal spacetherebetween.

In a filling/planarizing step shown in FIG. 4C, the internal spacesurrounded by the first optical resin layer 2 and the protective film 3is filled with a liquid resin having a second refractive index, and theliquid resin is cured, to form a microlens array between the firstoptical resin layer 2 and the protective film 3. In this embodiment, aresin having a high refractive index is injected under a vacuum in theinternal space between the first optical resin layer 2 and theprotective film 3, and is cured by heating. Alternatively, a UV-curedtype resin may be injected in the internal space and cured by UVirradiation. In this way, irregularities of the microlens planes formedon the surface of the first optical resin layer 2 are filled with theliquid resin having the second refractive index, and simultaneously thesurface, opposed to the microlens planes, of the resin is planarized.The resin is then cured, to form a second optical resin layer 6. Themicrolens array is thus formed by stacking the first optical resin layer2 and the second optical resin layer 6 different in refractive index toeach other. In this embodiment, since the liquid resin for forming thesecond optical resin layer 6 is injected in the gap between the glasssubstrate 1 and the support layer 4, the surface, opposed to themicrolens array, of the second optical resin layer 6 is automaticallyplanarized.

In a removing step shown in FIG. 4D, the support layer 4 made from thecover glass is removed by polishing or grinding with the protective film3 used as a stopper until only the protective film 3 remains on thesecond optical resin layer 6.

With the series of these steps, a microlens array with no cover glasscan be produced.

According to this embodiment, the joining step is performed before thefilling/planarizing step in order to form a gap required for the nextfilling/planarizing step. To be more specific, the support layer 4 isjoined to the first optical resin layer 2 with a specific gap kepttherebetween, and the liquid resin is injected in the gap and thencured. In this step, the surface, opposed to the microlens planes, ofthe resin is simultaneously planarized.

The method of producing a microlens array according to the presentinvention is not limited to this embodiment but may include a patterningstep of forming a first optical resin layer having a first refractiveindex on a transparent substrate and forming a plurality of microlensplanes arranged in a two-dimensional pattern on the surface of the firstoptical resin layer, a filling/planarizing step of filling theirregularities of the microlens planes with a resin having a secondrefractive index and planarizing the surface, opposed to the microlensplanes, of the resin, to form a second optical resin layer, a joiningstep of joining a support layer, on which a transparent protective filmis previously formed, to the planarized second optical resin layer, anda removing step of removing the support layer until only the protectivefilm remains on the second optical resin layer.

A second embodiment of the method of producing a microlens arrayaccording to the present invention will be described with reference toFIGS. 5A to 5C′. In this embodiment, the surface, opposed to a microlensarray, of a resin is planarized by a stamping method.

In a patterning step shown in FIG. 5A, a first optical resin layer 2having a first refractive index is formed on the surface of a glasssubstrate 1, and an Ni-electroformed original having a plurality ofmicrolens planes is stamped to the surface of the first optical resinlayer 2, to transfer the microlens planes to the surface of the firstoptical resin layer 2. Like the first embodiment, the first opticalresin layer 2 is made from a UV-cured type resin having a low refractiveindex. The first optical resin layer 2 is irradiated with ultravioletrays (wavelength: near 365 nm) at an energy of 3,000 mJ from the backside of the glass substrate 1, to cure the UV-cured type resin, therebyfixing the microlens planes transferred to the first optical resin layer2.

In a filling/planarizing step shown in FIG. 5B, the irregularities ofthe microlens planes are filled with a resin having a second refractiveindex, and the surface, opposed to the microlens planes, of the resin isplanarized by a flat stamper FS, to form a second optical resin layer 6.In this embodiment, a UV-cured type resin having a high refractive indexis dropped in the irregularities of the microlens planes, and thesurface, opposed to the microlens planes, of the resin is planarized bythe flat stamper FS. In such a state, the second optical resin layer 6is cured by UV irradiation, to fix the planarized surface of the secondoptical layer 6. In addition, the liquid resin may be supplied to theirregularities of the microlens planes by spin-coating in place ofdropping.

In a film formation step shown in FIG. 5C, a protective film 3 made fromSiO₂ or SiN is formed on the surface of the planarized second opticalresin layer 6 by CVD (Chemical Vapor Deposition) or sputtering, and thena transparent electrode 7 made from ITO (Indium Tin Oxide) is formed onthe surface of the protective film 3.

A step shown in FIG. 5C′ may be performed in place of the step shown inFIG. 5C. In this step, a thin cover glass layer 4 is bonded on theplanarized second optical resin layer 3, and the transparent electrode 7is formed on the cover glass layer 4. In this way, in the step shown inFIG. 5C′, the cover glass layer 4 is used in place of the protectivefilm 3 used in the step shown in FIG. 5C. If needed, the cover glasslayer 4 may be thinned by polishing or grinding.

According to this embodiment, a substrate for a liquid crystal display,which includes a microlens array integrated with the transparentelectrode, can be thus produced. Such a substrate is advantageous inthat since the surface of the microlens array is planarized, thesubstrate does not cause any unnecessary stress when being assembled ina liquid crystal display device. In particular, by adopting the stepshown in FIG. 5C, the microlens array without cover glass can beproduced. This is advantageous in reducing the production cost.

A third embodiment of the method of producing a microlens array will bedescribed with reference to FIGS. 6A to 6D. In this embodiment, thesurface, opposed to a microlens array, of a resin is planarized by aspin-coating method.

In a first spin coating step shown in FIG. 6A, after a first opticalresin layer 2 having a first refractive index is formed on a transparentglass substrate 1 and a plurality of microlens planes (depth: about 7μm) arranged in a two-dimensional pattern are formed on the surface ofthe first optical resin layer 2, first spin coating is performed. Inthis first spin coating, the microlens planes are coated with a liquidresin having a viscosity of about 100 cps at a rotating speed rangingfrom 500 to 1,000 rpm. As a result, a second optical resin layer 6 isformed on the bottoms of the microlens planes.

In a second spin coating step shown in FIG. 6B, second spin coating isperformed by re-coating the recessed microlens planes with a liquidresin having a viscosity of about 100 cps at a rotating speed rangingfrom 500 to 1,000 rpm.

In a third spin coating step shown in FIG. 6C, third spin coating isperformed by re-coating the recessed microlens planes with a liquidresin having a viscosity of 100 cps by a centrifugal force generated byrotation at a rotating speed ranging from 500 to 1,000 rpm. As a resultof repeating the spin coating by three times, the recessed microlensplanes are nearly filled with the second optical resin layer 6.

Finally, in a fourth spin coating step shown in FIG. 6D, fourth spincoating is performed so as to perfectly fill the microlens planes with aresin and planarize the surface, opposed to the microlens planes, of theresin. In this step, the rotating speed of a spin coater is set to ahigh value in a range of 3,000 to 5,000 rpm for smoothening the surface,opposed to the microlens planes, of the resin.

The spin coating method may be replaced by a spraying method. In thisspraying method, the viscosity of a liquid resin is set to a several tencps by using a solvent, and the liquid resin is sprayed while beingatomized into particles having sizes of several ten μm, and then dried.The spraying may be performed such that the particles of the liquidresin be flattened by surface tensions thereof. Such spraying and dryingof the resin are repeated. If any solvent is not used, a resin having alow viscosity may be used.

In addition to the above-described simple microlens array, a duelmicrolens array formed by stacking a microlens array functioning as acondenser lens to a microlens array functioning as a field lens has beendeveloped. As compared with a single microlens array, a duel microlensarray is advantageous in improving a utilization efficiency of light.

In a general three-panel type liquid crystal projector, the divergenceangle of light emitted from a light source and made incident on amicrolens array is often set to about 10°. In the case of using amicrolens array, since the divergence angle of light on the emergenceside of a liquid crystal panel becomes large, even if the divergenceangle of incident angle is made excessively large, the light is kickedby a projection lens, to rather reduce the utilization efficiency oflight. Also, from the viewpoint of preventing a reduction in contrastalong with an increase in divergence angle of light made incident on aliquid crystal panel, the incident angle is restricted to some extent.

On the contrary, in the case of a duel microlens array structure, sincea second lens (field lens) is disposed so as to be apart from a firstlens (condenser lens) by a focal distance of the second lens in thedirection of incident light, the divergence angle of light emerging froma (field lens arranged type) panel is controlled by the divergence angledue to a lens power of the duel microlens array, to reduce the degree ofkicking of light by a projection lens, thereby raising the utilizationefficiency of light.

Dual microlens arrays (DMLs) have two kinds of arrangement structuresfor the liquid crystal panels. In general, an active matrix type liquidcrystal panel has a stacked structure formed by joining a drivesubstrate provided with switching devices such as thin film transistors,pixel electrodes, and the like to a counter substrate provided with acounter electrode and holding liquid crystal between the drive substrateand the counter substrate. The first kind of the DML arrangementstructure is characterized in that a DML is disposed on the countersubstrate side. The second kind of the DML arrangement structure ischaracterized in that one microlens array of a DML is disposed on thecounter substrate side and the other microlens array of the DML isdisposed on the drive substrate side, wherein liquid crystal is heldtherebetween.

Such a DML must cope with the tendency toward high definition of pixels.To reduce panel sizes, pixel sizes must be reduced in proportion to thereduced panel sizes, and correspondingly, an arrangement pitch ofindividual microlenses must be reduced. As a result, it is required toshorten the focal distances of microlenses and also to thin a coverglass. Of these requirements, the shortening of the focal distances ofmicrolenses can be relatively easily realized; however, the thinning ofa cover glass is more difficult than that in the case of a singlemicrolens array.

The DML structure is generally produced by sticking two pieces of singlemicrolens arrays (SMLs) to each other. In this case, to meet therequirement toward high definition, the thickness and the like of eachof a cover glass and an optical resin layer in each SML must be morestrictly controlled than those in an ordinary SML.

A basic configuration of a liquid crystal display device (liquid crystalpanel) in which a DML is formed on the counter substrate side and aproblem thereof to be solved will be described with reference to FIG. 7.As shown in the figure, a liquid crystal display device has a stackedstructure formed by joining a drive substrate 10 to a counter substrate20 by a seal material 31, and enclosing liquid crystal in a gap betweenboth the substrates 10 and 20. The drive substrate 10 is formed of aglass base 11, on the surface of which switching devices such as thinfilm transistors and pixels 12 including pixel electrodes are integratedin a matrix pattern. The pixels 12 are partitioned from each other by alattice-shaped black matrix 13.

A dual microlens array DML and a counter electrode (not shown) areformed on the counter substrate 20. The DML is held between a glasssubstrate 21 and a cover glass 22, and has a stacked structure formed bystacking a low refractive index resin layer 23, a high refractive indexresin layer 24, and a low refractive index resin layer 25 to each other.The low refractive index resin layers 23 and 25 are each made from afluorine-based resin, a silicon-based resin, or an acrylic-based resin,and the high refractive index resin layer 24 is made from anacrylic-based resin, an epoxy-based resin, or a thiourethane-basedresin. A first ML (condenser lens) is formed at the interface betweenthe low refractive index resin layer 23 and the high refractive indexresin layer 24, and a second ML (field lens) is formed at the interfacebetween the high refractive index resin layer 24 and the low refractiveindex resin layer 25.

As the pixel pitch becomes narrow along with the tendency toward highdefinition of pixels, it becomes important to improve control andaccuracy of a distance {circle around (1)} between the principal pointof the second ML and the surface of the cover glass 22, a distance{circle around (2)} between the principal point of the first ML and theprincipal point of the second ML, and an alignment value {circle around(3)} between the first ML and the second ML. These parameters {circlearound (1)}, {circle around (2)}, and {circle around (3)} determine thelight collection ratio of the DML. Of these parameters, the distance{circle around (2)} between the principal point of the first ML and theprincipal point of the second ML is required to be strictly controlledfor realizing the function of the field type DML.

FIG. 8 is a graph showing a dependency of a light collection ratio onthe parameter {circle around (1)} (distance between the principal pointof the second ML and the surface of the cover glass). It is to be notedthat the light collection ratio is expressed in effective aperture ratioof pixels. As is apparent from the graph, to obtain a very high value ofthe light collection ratio, it is preferred to set the parameter {circlearound (1)} in a range of about 5 μm or less, and to keep a relativelyhigh value of the light collection ratio, it is preferred to set theparameter {circle around (1)} in a range of 10 μm or less. Accordingly,it is required to make the thickness of the cover glass 22 of the secondML very thin. The graph of FIG. 8 shows two curves different inparameters. Even on the basis of either of these curves, it is apparentthat the parameter {circle around (1)} should be suppressed in the rangeof 10 μm or less. It is to be noted that the graph of FIG. 8 is obtainedby plotting data measured under a condition that the pixel pitch is setto 18 μm×18 μm and the divergence angle of light emitted from a lightsource and made incident on the panel is set to 10°.

2. Liquid Crystal Display Device

A first embodiment of a liquid crystal display device according to thepresent invention will be described with reference to FIGS. 9A to 9E.

FIGS. 9A to 9E are typical process diagrams showing steps of forming aliquid crystal display device in this embodiment.

This embodiment is characterized in that a dual microlens array isformed on the counter substrate side.

FIG. 9A shows the step of preparing a first ML substrate and a second MLsubstrate. A resin layer 23 having a low refractive index, on thesurface of which microlens planes are previously formed by a stampingmethod, is formed on a first ML substrate 21. A protective film 26 isformed as a polishing stopper on a second ML substrate 22, and a resinlayer 25 having a low refractive index, on the surface of whichmicrolens planes are previously formed by a stamping method, is formedon the protective film 26. The protective film 26 is made from Al₂O₃ ora-DLC. At the time of polishing the second ML substrate 22 in thesubsequent step, the protective film 26 functions as a stopper capableof ensuring the uniformity of polishing. The film made from Al₂O₃ ora-DLC is transparent, and may have a thickness of about 100 nm or moreto function as an effective stopper. The protective film 26 can beformed by a sputtering process or a PECVD (Plasma Enhanced ChemicalVapor Deposition) process. The stopper film is not necessarilytransparent. For example, the stopper film may be formed by depositinga-Si or the like to a thickness of about 1 μm. The microlens planesformed on each of the low refractive index resin layers 23 and 25 haveaspheric shapes (ellipsoids or hyperboloids) having a curvature radiusand an aspheric constant specified so as to be matched with a pixelpitch and thereby to obtain the maximum light correction efficiency.

FIG. 9B shows the step of joining the first ML substrate and the secondML substrate to each other. An outer peripheral portion of one of thefirst ML substrate 21 and the second ML substrate 22 is coated with aseal material 27 composed of an epoxy resin or acrylic resin. Afteralignment marks of the first ML substrate 21 and the second ML substrate22 are aligned with each other, the first ML substrate 21 and the secondML substrate 22 are overlapped to each other. The epoxy resin or acrylicresin used for the seal material 27 is of a UV-cured type or aUV-cured/thermally-cured combination type. The resin used as the sealmaterial 27 previously contains glass fibers or plastic beads as aspacer in an amount of 1 to 5 wt % in order to make the distance betweenthe principal point of the first ML and the principal point of thesecond ML correspond to the focal distance of the second ML. Forexample, if pixels are arranged with a pixel pitch of 18 μm, the focaldistance (equivalent value in air) of the first ML is about 65 μm andthe focal distance (equivalent value in air) of the second ML is about40 μm; and the aspheric constant K of each of the first ML and thesecond ML is about −1.3. In addition, the refractive index of the lowrefractive index resin is set in a range of 1.41 to 1.45 and therefractive index of a high refractive index resin to be described lateris set in a range of 1.60 to 1.66. In this case, to satisfy thecondition of field arrangement, the distance (equivalent value in air)between the principal point of the first ML and the principal point ofthe second ML is required to be set to about 40 μm. Accordingly, in thecase of filling a gap between the first and second ML substrates 21 and22 with a high refractive index resin having a refractive index of 1.60in the subsequent step, the thickness of the sealing material 27 may beset to a value capable of ensuring a gap dimension of about 40/1.6=25μm. Concretely, the particle size of plastic beads contained in the sealmaterial 27 may be nearly set to a value calculated from an equation of[25 μm−(D1+D2)] where D1 is the thickness of the low refractive indexresin layer 23 and D2 is the thickness of the low refractive index resinlayer 25 as shown in FIG. 9B. In actual, such determination of thethickness of the seal material 27 must be made in consideration ofdepression of the resin at the time of pressing the resin.

FIG. 9C shows the step of forming a duel microlens array between thefirst and second ML substrates. A high refractive index resin 24 isinjected under vacuum in a gap between the first ML substrate 21 and thesecond ML substrate 22 joined to each other by the seal material 27, toform a duel microlens array. In the case of a pixel pitch of 14 μm, analignment accuracy between the first ML substrate 21 and the second MLsubstrate 22 is preferably set in a range of less than ±1.0 μm. The highrefractive index resin 24 injected between the first ML substrate 21 andthe second ML substrate 22 is cured by heating. If the resin 24 is of aUV-cured type resin, the resin 24 is cured by UV irradiation. If needed,the resin 24 may be kept in a liquid state between the first MLsubstrate 21 and the second ML substrate 22.

FIG. 9D shows the step of removing the second ML substrate by polishingor grinding. The second ML substrate 22 is removed by polishing orgrinding until the removal depth reaches the protective film 26functioning as the stopper. Concretely, the second ML substrate 22 maybe polished by a CMP (Chemical-Mechanical Polishing) process using, forexample, Ce₂O₃. If the protective film 26 is made from a-Si (amorphoussilicon), after the a-Si film (protective film) 26 functioning as thestopper is exposed by polishing, the a-Si film 26 can be removed bypolishing using silica.

By the removal of the second ML substrate 22, a structure having the DMLon the counter substrate side can be obtained. In this step, since thepolishing is performed with the protective film used as the stopper, itis possible to perfectly remove the second ML substrate (cover glass),and also to increase the uniformity of polishing and hence to improvethe light utilization efficiency and the image quality.

FIG. 9E shows the step of finishing a liquid crystal display device. Acounter electrode 28 is formed on the surface, exposed by polishing, ofthe protective film 26, to obtain a counter substrate 20 integrated withthe DML. A drive substrate 10 is joined to the counter substrate 20 viaa seal material 31, and liquid crystal 30 is enclosed in a gaptherebetween, to obtain a liquid crystal display device. In addition,switching devices such as thin film transistors (TFTs) and pixelelectrodes are previously integrated on the surface of the drivesubstrate 10.

As described above, the liquid crystal display device according to thisembodiment has a panel structure including the drive substrate 10 onwhich at least pixel electrodes and switching devices for driving thepixel electrodes are formed, the counter substrate 20 on which at leastthe counter electrode 28 is formed, and the liquid crystal layer 28disposed between both the substrates 10 and 20 joined such that thepixel electrodes are opposed to the counter electrode 28 with a specificgap put therebetween. The microlens array composed of the microlensesarranged in a two-dimensional pattern corresponding to the arrangementpattern of the pixel electrodes is assembled at least in the countersubstrate 20.

As the feature of the liquid crystal display device according to thisembodiment, the microlens array has the back surface joined to the firstML substrate 21 constituting the counter substrate 20 and the planarizedfront surface.

The counter electrode 28 is formed on the planarized surface of themicrolens array via the protective film 26. To be more specific, theprotective film 26 previously formed on the support (second ML substrate22) is bonded on the planarized surface of the microlens array, theprotective film 26 is exposed by removing the support (second MLsubstrate 22), and the counter electrode 28 is formed on the exposedprotective film 26. As described above, the protective film 26 can bemade from Al₂O₃, a-DLC, TiO₂, SiN, or Si.

According to this embodiment, the microlens array is configured as aduel microlens array of a double structure having a first microlensarray which is disposed on the side apart from the liquid crystal layer30 and which functions as a condenser lens, and a second microlens arraywhich is disposed on the side close to the liquid crystal layer 30 andwhich functions as an approximately field lens. The distance between theprincipal point of each microlens of the second microlens array and theliquid crystal layer 30 is specified to be in a range of 10 μm or less.

FIGS. 10A to 10E are process diagrams showing steps of forming a liquidcrystal display device as a reference example. In these figures, for aneasy understanding, parts corresponding to those of the liquid crystaldisplay device according to the embodiment shown in FIGS. 9A to 9E aredenoted by the same reference numerals.

This reference example is different from the embodiment shown in FIGS.9A to 9E in that any protective film functioning as a polishing stopperis not interposed between a second ML substrate (cover glass) and a lowrefractive index resin layer.

In a step shown in FIG. 10A, a first ML substrate 21 and a second MLsubstrate 22 are disposed opposite to each other; in a step shown inFIG. 10B, the first ML substrate 21 and the second ML substrate 22 arejoined to each other by a seal material 27; and in a step shown in FIG.10C, a gap between the first ML substrate 21 and the second ML substrate22 joined to each other is filled with a high refractive index resin 24.A duel microlens array is thus formed.

In a step shown in FIG. 10D, the second ML substrate (cover glass) 22 isremoved by polishing or grinding. In this step, as described above, bythinning the thickness of the cover glass to about 10 μm, the distance(equivalent value in air) between the principal point of the second MLand the surface of the cover glass can be substantially set to a valuein a range of 5 μm or less. However, in the case of thinning the coverglass to about 10 μm by polishing without using any stopper, since theremaining thickness of the cover glass becomes too thin, the cover glassmay be often obliquely polished as shown in FIG. 10D′, or during thepolishing step, the cover glass may be cracked, leading to breakagethereof. This causes a variation in light collection efficiency or astray of the boundary between the glass and resin in an image uponprojection thereof, to thereby significantly degrade the image quality.

In a step shown in FIG. 10E, a counter electrode (not shown) made fromITO or the like is formed on the polished surface of the second MLsubstrate 22, to form a counter substrate 20, and the counter substrateis joined to a drive substrate 10 and then liquid crystal 30 is enclosedin a gap therebetween, to obtain a liquid crystal panel. For the liquidcrystal panel thus obtained, if the thickness of the second ML substrate22 is not uniformly polished, such a liquid crystal panel may cause astray of the boundary between the cover glass 22 and the low refractiveindex resin layer 25 in an image upon projection thereof, to therebysignificantly degrade the image quality.

A second embodiment of the liquid crystal display device according tothe present invention will be described with reference to FIGS. 11A to11E.

FIGS. 11A to 11E are process diagrams showing steps of forming a liquidcrystal display device in this embodiment.

This embodiment is characterized in that a dual microlens array isformed on the counter substrate side, and that the method of forming asingle microlens array (SML) shown in FIGS. 4A to 4D are applied to amethod of forming a duel microlens array.

FIG. 11A shows the step of forming a first microlens array and a secondmicrolens array.

An optical resin layer 23 a is formed on a first support 21 and firstmicrolens planes arranged in a two-dimensional pattern are formed on thesurface of the optical resin layer 23 a. The irregularities of the firstmicrolens planes are filled with an optical resin 23 having a refractiveindex different from that of the optical resin layer 23 a, and thesurface, opposed to the microlens planes, of the optical resin 23 isplanarized, to thereby form a first microlens array. In this embodiment,the optical resin 23 used to fill the irregularities of the microlensplanes has a low refractive index such as about 1.4. The surface of theoptical resin 23 may be planarized by the above-described stampingmethod, spin-coating method, or spraying method.

Similarly, a protective film 26 functioning as a polishing stopper isformed on a second support 22 and an optical resin layer 25 a is formedon the protective film 26, and then second microlens planes arranged ina two-dimensional pattern are formed on the surface of the optical resinlayer 25 a. The irregularities of the second microlens planes are filledwith an optical resin 25 having a refractive index different from thatof the optical resin layer 25 a, and the surface, opposed to themicrolens planes, of the optical resin 25 is planarized, to form asecond microlens array. The optical resin 25 also has a low refractiveindex of about 1.4. The surface of the optical resin 25 filling themicrolens planes may be planarized by the above-described stampingmethod, spin-coating method, or spraying method.

FIG. 11B shows the step of overlapping the first and second microlensarrays. An outer peripheral portion of one of the supports 21 and 22 iscoated with a seal material 27. The supports 21 and 22 are aligned toeach other on the basis of alignment marks and overlapped to each other.The seal material 27 contains a spacer such as high accurate plasticfibers so as to keep the thickness of the seal material 27 in a range of10 μm or less.

FIG. 11C shows the step of integrating the first and second microlensarrays with each other. The planarized surface of the first microlensarray is joined to the planarized surface of the second microlens arrayin a state that the first microlens planes are aligned to the secondmicrolens planes, to integrate both the microlens arrays with eachother. As a result, a gap equivalent to the thickness of the sealmaterial 27 is formed between the supports 21 and 22.

FIG. 11D shows the step of forming a duel microlens array by injecting aresin in the gap. A high refractive index resin 24 having a refractiveindex of about 1.6, which resin is in a liquid state, is injected in thegap specified by the thickness of the seal material 27. The resin 24 isthen cured by heating, to form a duel microlens array. It is preferredto very slowly cure the high refractive index resin 24 filling the gapin order that stress does not remain in the resin 24. The support 22 isremoved by polishing with the protective film 26 used as the polishingstopper, to expose the surface of the protective film 26. A counterelectrode made from ITO or the like is formed on the surface of theexposed protective film 26, to form a counter substrate 20.

FIG. 11E shows the step of finishing a liquid crystal display device.The counter substrate 20 is joined to a previously prepared drivesubstrate 10, and liquid crystal is enclosed therebetween. In this way,a liquid crystal panel is obtained.

According to this embodiment, since the single microlens arrays each ofwhich is previously planarized are joined to each other, it is possibleto obtain a high accurate duel microlens array structure with no stress.

FIG. 12 is a reference diagram showing a general configuration of aliquid crystal display device having a DML structure in which onemicrolens array is disposed on the counter substrate side and the othermicrolens array is disposed on the drive substrate side. A liquidcrystal display device shown in the figure has a panel structure that adrive substrate 10 and a counter substrate 20 are joined to each otherby a seal material 31 and liquid crystal is enclosed therebetween. Thecounter substrate 20 is composed of a glass substrate 21 and a coverglass 22. A first ML is interposed between the glass substrate 21 andthe cover glass 22, wherein the first ML functions as a condenser lensis located on the incident side. The first ML is formed by stackingresin layers 23 and 24 different in refractive index to each other.

The drive substrate 10 is generally composed a TFT substrate 11 on whichthin film transistors and pixel electrodes are integrated. The TFTsubstrate 11 is generally thinned by polishing. Pixels 12 are integratedon the surface of the TFT substrate 11. The pixels 12 are partitionedfrom each other by a lattice-shaped black matrix 13. A second MLfunctioning as a field lens is interposed between the TFT substrate 11and an auxiliary substrate on the back side. The second ML is alsoformed by stacking resin layers 15 and 16 different in refractive indexto each other.

In the liquid crystal panel having such a DML structure, the thickness{circle around (1)} of the TFT substrate 11 after polishing, thedistance {circle around (2)} between the principal point of the first MLand the principal point of the second ML, and the alignment accuracy{circle around (3)} between the first ML and the second ML are importantfunction parameters.

The parameter {circle around (2)}, which is the distance between theprincipal point of the first ML and the principal point of the secondML, is required to correspond to the focal distance of the second ML inorder to realize the so-called field arrangement. In actual, if there isan offset of about 10% between the distance between both the principalpoints and the focal distance of the second ML, the second ML acts as anapproximately field lens. For this purpose, the parameter {circle around(1)}, which is the thickness of the TFT substrate 11 after polishing, isrequired to be as small as about 10 to 50 μm.

With respect to formation of the TFT substrate having such a smallthickness, however, there arise problems that the TFT substrate maycause cracking or chipping during polishing, and also may cause strainor wrinkle due to shrinkage upon curing of a resin during formation ofthe second ML.

As will be described below, such problems can be solved by making use ofthe above-described planarizing technique according to the presentinvention.

To improve the luminance of a liquid crystal projector, the structurethat one of the microlens arrays of the DML is formed on the drivesubstrate side and the other is formed on the counter substrate side asshown in FIG. 9 is superior to the structure that the microlens arraysof the DML are both formed on the counter substrate side.

In the case of forming the microlens arrays of the DML on the countersubstrate side, although light is effectively collected by the microlensarrays of the DML, the collected light may be kicked by a non-effectiveresin such as a black matrix surrounding the pixels on the drivesubstrate side, to reduce the effective aperture ratio. On the contrary,in the structure that one of the microlens arrays of the DML is disposedon the drive substrate side and the other is disposed on the countersubstrate side, by shortening the focal distance of the first ML, it isallowed for light emitted from a light source to be collected as much aspossible, and it is allowed for such a large quantity of collected lightto pass through pixel apertures on the TFT substrate side. Meanwhile,the second ML is disposed as a field lens while being opposed to thefirst ML with the TFT substrate put therebetween in such a manner thatthe principal point of the second ML is apart from the principal pointof the first ML by the focal distance of the second ML.

A third embodiment of the liquid crystal display device according to thepresent invention will be described with reference to FIGS. 13A to 13F.

FIGS. 13A to 13F are process diagrams showing steps of forming a liquidcrystal display device in this embodiment.

This embodiment is characterized in that one of microlens arrays of aDML structure is disposed on the drive substrate side and the other isdisposed on the counter substrate side.

FIG. 13A shows the step of preparing a TFT substrate. A TFT substrate 11on which TFTs and pixel electrodes are previously formed is prepared. Inthe figure, only a black matrix 13 for partitioning pixels from eachother is shown, with TFTs and pixel electrodes not shown.

FIG. 13B shows the step of sticking a base glass to the TFT substrate. Abase glass 40 is stuck on the surface of the TFT substrate 11 via anadhesive 41 such as wax.

FIG. 13C shows the step of polishing the TFT substrate. The back surfaceof the TFT substrate 11 in a state being held by the base glass 40 ispolished to a thickness of 20 μm or less.

FIG. 13D shows the step of preparing a glass substrate with a second ML.A glass substrate 14 on which a second ML is previously formed isprepared. The second ML has a structure formed by stacking resin layers15 and 16 different in refractive index to each other. The surface,opposed to microlens planes, of the second resin layer 16 is planarizedby the above-described stamping method or spin-coating method. Aperipheral portion of the polished back surface of the TFT substrate 11is coated with a seal material 18 having a thickness of 2 to 3 μm.

FIG. 13E shows the step of forming a drive substrate by joining the TFTsubstrate to the glass substrate. In a state that pixels formed on theTFT substrate 11 side are aligned to the second ML formed on the glasssubstrate 14 side, the TFT substrate 11 is overlapped to the glasssubstrate 14. A gap between both the overlapped substrates 14 and 11 isfilled with an adhesive 19, to join both the substrates 14 and 11 toeach other. Here, since the planarized surface of the second ML isjoined to the polished back surface of the TFT substrate 11, it ispossible to solve the related art problem associated with stress. Adrive substrate 10 integrated with the second ML is thus obtained. Sincethen, the unnecessary base glass 40 is removed, and the adhesive such aswax remaining on the surface of the TFT substrate 11 is separated.

FIG. 13F shows the step of finishing a liquid crystal display device. Acounter substrate 20 to which a first ML is previously integrated isprepared. The counter substrate 20 includes a glass substrate 21, acover glass 22, and the first ML held therebetween. The first ML has astacked structure formed by stacking resin layers 23 and 24 different inrefractive index to each other. The counter substrate 20 integrated withthe first ML is joined to the drive substrate 10 integrated with thesecond ML, and liquid crystal is enclosed in a gap therebetween, toobtain a liquid crystal display device. The first ML incorporated in thecounter substrate 20 functions as a condenser lens, and the second MLformed on the drive substrate 10 functions as a field lens.

As described above, the liquid crystal display device shown in FIGS. 13Ato 13F has the panel structure including the drive substrate 10 on whichat least pixels electrodes and the switching devices for driving thepixel electrodes are formed, the counter substrate 20 on which at leasta counter electrode is formed, and the liquid crystal layer disposedbetween both the substrates 10 and 20 joined such that the pixelselectrodes are opposed to the counter electrode with a specific gap kepttherebetween.

The microlens array composed of microlenses arranged in atwo-dimensional pattern corresponding to the arrangement pitch of thepixel electrodes is incorporated at least in the drive substrate 10. Themicrolens array (second ML) has the stacked structure including thefirst optical resin layer 15 which has a first refractive index andwhich has the microlens planes arranged in a two-dimensional pattern,and the second optical resin layer 16 which has a second refractiveindex and which fills the irregularities of the microlens planes and hasthe planarized surface. The microlens array (second ML) is joined to theTFT substrate 11 such that the planarized surface of the second opticalresin layer 16 is in contact with the back surface of the TFT substrate11. The microlens array (second ML) is obtained by filling the microlensplanes of the first optical resin layer 15 with the resin (for formingthe second optical resin layer 16) and pressing the surface of the resinwith a stamper having a flat plane, to planarize the surface, opposed tothe microlens planes, of the second optical resin layer 16.Alternatively, the planarization may be performed by making use of theabove-described polishing technique in place of stamping using thestamper. The polishing technique includes the steps of joining a supportlayer, on which a protective layer as a polishing stopper is previouslyformed, to the first optical resin layer with a specific gap kepttherebetween; filling the gap with a liquid resin and curing the resin,to form the second optical resin layer; and removing the support layerby polishing, to expose the protective layer. In this technique, theexposed surface of the protective layer is taken as the planarizedsurface of the second optical resin layer.

According to this embodiment, the microlens array (first ML) is disposedin the counter substrate 20 in such a manner as to be matched with themicrolens array (second ML) disposed in the drive substrate. Themicrolens array (first ML) functions as a condenser lens and themicrolens array (second ML) functions as a field lens. The TFT substrate11 of the drive substrate 10 is polished from the back side to bethinned. The planarized surface of the second optical resin layer 16 ofthe microlens array (second ML) is joined to the polished back surfaceof the TFT substrate 11.

FIG. 14A is a typical sectional view showing a finished state of theliquid crystal display device shown in FIGS. 13A to 13F, and FIG. 14B isa partial enlarged view of FIG. 14A.

As described above, the second ML is joined to the polished back surfaceof the TFT substrate 11 via a thin layer of the adhesive 19. Here, it isparticularly important to join the previously planarized surface of thesecond ML to the back surface of the thinned TFT substrate 11.

For example, in the case where the TFT substrate 11 is used for a 0.7inch TFT substrate (pixel pitch: 18 μm) for SVGA (Super Video GraphicsArray), if the focal distance (equivalent value in air) of a first ML isabout 35 μm and the focal distance (equivalent value in air) of a secondML is about 42 μm, the distance (equivalent value in air) between theprincipal point of the first ML and the interface of a liquid crystallayer 30 is about 20 μm, the thickness (equivalent value in air) of theliquid crystal layer 30 is 2 μm, and the distance (equivalent value inair) between the interface of a liquid crystal layer 30 and theprincipal point of the second ML is about 20 μm. In this case, thethickness of the TFT substrate 11 is thinned by polishing to an actualthickness of about 27 μm (equivalent value in air: about 18 μm). In thisway, the TFT substrate 11 is very thin, and therefore, if a highrefractive index resin 16 is solidified by UV-curing or thermal curingin a state being in contact with the TFT substrate 11 as in the relatedart method, the TFT substrate 11 causes strain due to stress generatedupon curing. Such strain exerts adverse effect on the image quality.

To cope with such an inconvenience, according to the present invention,the previously planarized surface of the second ML is stuck on the backsurface of the TFT substrate 11, to thereby suppress occurrence ofstress.

As shown in FIG. 14B, the thicknesses of the resin layer 16 of thesecond ML are different at locations A, B and C. If the second ML isjoined to the TFT substrate 11 in a state that the surface of the resinlayer 16 is not planarized, the shrinkage volume of the resin layer 16upon curing locally differs, to cause strain in the TFT substrate 11.

A fourth embodiment of the liquid crystal display device according tothe present invention will be described with reference to FIGS. 15A to15F.

FIGS. 15A to 15F are process diagrams showing steps of forming a liquidcrystal display device in this embodiment.

This embodiment is characterized in that one of microlens arrays of aDML structure is disposed on the drive substrate side and the other isdisposed on the counter substrate side.

FIG. 15A shows the step of preparing a finished liquid crystal panel. Afinished liquid crystal panel 50, which has a stacked structure formedby stacking a counter substrate 20 to a TFT substrate 11 and enclosingliquid crystal 30 therebetween, is prepared. The counter substrate 20has a thickness of, for example, 1.1 mm and incorporates a first ML. TheTFT substrate 11 has a thickness of 0.8 to 1.2 mm, on the surface ofwhich TFTs and pixel electrodes are integrated.

FIG. 15B shows the step of stacking a jig to the counter substrate. Ajig 40 made from blue plate glass is stuck on the counter substrate 20side with wax.

FIG. 15C shows the step of polishing the TFT substrate. In a state thatthe panel is held by the jig 40, the back surface of the TFT substrate11 is polished until the thickness of the TFT substrate 11 becomes about10 to 20 μm.

FIG. 15D shows the step of preparing a glass substrate having a secondML. A peripheral portion of the polished back surface of the TFTsubstrate 11 is coated with a seal material 18, and at the same time, aglass substrate 14 on which a second ML is previously formed isprepared. The second ML has a stacked structure formed by stackingoptical resin layers 15 and 16 different in refractive index to eachother.

FIG. 15E shows the step of joining the liquid crystal panel to the glasssubstrate. The liquid crystal 50 is aligned to the glass substrate 14,and is then joined thereto via the adhesive (seal material) 18. At thistime, the glass substrate 14 integrated with the second ML is joined tothe polished back surface of the TFT substrate 11, to form a drivesubstrate 10. A high refractive index resin 19 is injected in a gapbetween the TFT substrate 11 and the planarized surface of the secondML.

FIG. 15F shows the step of removing the jig. The unnecessary jig 40 isfinally removed.

A panel having a structure that the counter substrate 20 integrated withthe first ML is joined to the drive substrate 10 incorporating thesecond ML, and the liquid crystal 30 is enclosed therebetween is thusobtained. With this panel, since the surface of the second ML isplanarized and the thickness of the resin layer 19 is as very thin ascomparable to that of the liquid crystal layer 30, it is possible toprevent occurrence of stress due to shrinkage upon curing the resin.

A fifth embodiment of the liquid crystal display device according to thepresent invention will be described with reference to FIG. 16.

FIG. 16 is a typical sectional view showing optical characteristics of aliquid crystal display device in this embodiment, which has a panelstructure that one of a pair of microlens arrays is disposed on thecounter substrate side and the other is disposed on the drive substrateside. To be more specific, lens planes having a light condensingfunction are disposed on the counter substrate side, and lens planeshaving a field function are disposed on the TFT substrate (drivesubstrate) side. The liquid crystal panel includes a TFT substrate 50B,and a counter substrate 50A disposed on the light incident plane side ofthe TFT substrate 50B in such a manner as to be opposed to the TFTsubstrate 50B with a liquid crystal layer 45 put therebetween.

The counter substrate 50A has a glass substrate 41, a resin layer 43A, afirst microlens array 42A, and a thinned counter substrate 44A, whichare arranged in this order from the light incident side. The TFTsubstrate 50B has pixel electrodes 46, a black matrix 47, a thinned TFTsubstrate 44B, a second microlens array 42B, a resin layer 43B, and aglass substrate 48, which are arranged in this order from the lightincident side.

The first microlens array 42A is made from an optical resin, and has aplurality of first microlens 42M-1 arranged in a two-dimensional patterncorresponding to an arrangement pattern of the pixel electrodes 46. Eachmirolens 42M-1 has a first lens plane R1 having a positive power andfunctions as a condenser lens. In this embodiment, a refractive index n1of the resin layer 43A and a refractive index n2 of the first microlensarray 42A satisfy a relation of n2>n1, and the first lens plane R1 isconvex toward the light incident side (light source side).

Like the first microlens array 42A, the second microlens array 42B ismade from an optical resin, and has a plurality of second microlenses42M-2 arranged in a two-dimensional pattern corresponding to anarrangement pattern of the pixel electrodes 46. Each microlens 42M-2 hasa second lens plane R2 having a positive power and functions as a fieldlens. Accordingly, the focal point of the second lens plane R2 of thesecond microlens 42M-2 nearly corresponds to the principal point of thefirst lens plane R1 of the first microlens 42M-1 (see an optical pathshown by a dotted line in the figure). In this embodiment, a refractiveindex n4 of the resin layer 43B and a refractive index n3 of the secondmicrolens array 42B satisfy a relation of n4>n3, and the second lensplane R2 is convex toward the light incident side.

A duel microlens array in this embodiment has a structure that eachpixel aperture is positioned between both the microlenses 42M-1 and42M-2, more specifically, between both the lens planes R1 and R2. On anoptical axis 60, the synthesized focal point of both the microlenses42M-1 and 42M-2 is located near the pixel aperture (see an optical pathshown by a solid line in the figure). The alignment of the synthesizedfocal point to the pixel aperture can be controlled by adjusting thethickness between each of the microlenses 42M-1 and 42M-2 and the pixelaperture. Such a configuration is best for enhancing the effectiveaperture ratio; however, it has been regarded to be produced with themost difficulty. According to the present invention, it is possible toovercome such a difficulty in production and to realize the duelmicrolens array structure shown in the figure.

A sixth embodiment of the liquid crystal display device according to thepresent invention will be described with reference to FIG. 17.

FIG. 17 is a typical sectional view showing the entire configuration ofa liquid crystal display device having a panel structure in thisembodiment.

This embodiment is characterized by realizing a small-sized liquidcrystal panel with a high definition characteristic.

A liquid crystal panel shown in the figure is configured such that acounter substrate 20 is stuck on a drive substrate 10 with a specificgap kept therebetween and liquid crystal 30 is enclosed in the gap. Asdescribed above, a microlens ML functioning as a condenser lens isformed in the counter substrate 20, and a microlens ML functioning as afield lens is integrated to the drive substrate 10.

Scanning lines 104 and signal lines 105, which are perpendicular to eachother, are provided on the inner surface of the drive substrate 10.Pixel electrode 106 and thin film transistors (TFT) as pixel switchesare arranged in a matrix at respective intersections at which the lines104 and 105 cross each other. While not shown, an alignment film havingbeen subjected to rubbing treatment is formed on the inner surface ofthe drive substrate 10. A counter electrode 112 is formed on the innersurface of the counter substrate 20. While not shown, an alignment filmhaving been subjected to rubbing treatment is also provided on the innersurface of the counter electrode 112.

Polarizing plates 110 and 111 are disposed on both the outer sides ofthe assembly of the drive substrate 10 and the counter substrate 20joined to each other, wherein the polarizing plate 110 is located on thedrive substrate 10 side with a specific gap kept therebetween and thepolarizing plate 111 is located on the counter substrate 20 side with aspecific gap kept therebetween. A scanning pulse is applied to ascanning line 104, to select the TFTs along the scanning line 104, and asignal is supplied to a signal line 105, to be written on the pixelelectrode 106 located at the intersection between the scanning line 104and the signal line 105. A voltage is applied between such a pixelelectrode 106 and the counter electrode 112, to activate the liquidcrystal 30. A change in transmission amount of incident white light dueto activation of the liquid crystal layer 30 is taken out through a pairof the polarizing plates 110 and 111 set in a cross nicol position, toperform a desired image display.

A projector is configured by projecting such an image display to ascreen located in front of the liquid crystal panel via an enlargedprojection optical system. If such a projector adopts a duel microlensarray structure having a combination of the microlens array functioningas a condenser lens and the microlens array functioning as a field lens,it is expected to improve the utilization efficiency of light emittedfrom a light source and to obtain a screen with a high luminance.

The projector to which the present invention is applied will bedescribed below.

3. Projector

An embodiment of a projector of the present invention will be describedwith reference to FIG. 18. FIG. 18 is a typical diagram showing aprojector incorporating the liquid crystal panel shown in FIG. 17. Theprojector shown in the figure is of a so-called three-panel type inwhich a color image display is performed by using three pieces oftransmission type liquid crystal panels, wherein each liquid panelincorporates a microlens array configured according to the presentinvention.

The projector in this embodiment includes a light source 211, a pair offirst and second multi-lens array integrators 212 and 213, and afull-reflection mirror 214 disposed between the first and secondmulti-lens array integrators 212 and 213 in such a manner that anoptical path (optical axis 210) is turned at an approximately 90° on thesecond multi-lens array integrator 213 side. A plurality of microlenses212M are arranged in a two-dimensional pattern in the first multi-lensarray integrator 212, and similarly a plurality of microlenses 213M arearranged in a two-dimensional pattern in the second multi-lens arrayintegrator 213. Each of the multi-lens array integrators 212 and 213 isintended to equalize a light illuminance distribution, and has afunction of dividing incident light into a plurality of small lightfluxes.

The light source 211 emits white light containing a red light component,a blue right component, and a green light component required for colorimage display. The light source 211 is composed of an emitter (notshown) for emitting light, and a concave mirror for reflecting andcollecting the light emitted from the emitter. Examples of the emittersinclude a halogen lamp, a metal lamp, and a xenon lamp. The concavemirror preferably has a shape capable of enhancing the light collectionefficiency, for example, a rotation-symmetric shape such as an ellipsoidof revolution or a paraboloid of revolution.

The projector also includes a PS synthesizing element 215, a condenserlens 216, and a dichroic mirror 217 arranged in this order on the lightemergence side of the second multi-lens array integrator 213 side. Thedichroic mirror 217 has a function of separating incident light, forexample, into a red light component LR and the other color lightcomponent.

The PS synthesizing element 215 is provided with a plurality ofhalf-wave plates 215A at positions each of which corresponds to a gapbetween adjacent two of the microlenses of the second multi-lens arrayintegrator 213. The PS synthesizing element 215 has a function ofseparating incident light L0 into two kinds of polarized lightcomponents (P-polarized light component and S-polarized light component)L1 and L2. The PS synthesizing element 215 also has a function of makingthe polarized light component L2 (for example, P-polarized lightcomponent) emergent from the PS synthesizing element 215 while keepingthe polarization direction thereof, and converting the polarized lightcomponent L1 (for example, S-polarized light component) into the otherpolarized light component (for example, P-polarized light component) bythe function of the half-wave plates 215A.

The projector also includes a full-reflection mirror 218, a field lens224R, and a liquid crystal panel 225R in this order along an opticalpath of the red light component LR separated by the diachronic mirror217. The full-reflection mirror 218 reflects the red light component LRseparated by the dichroic mirror 217 to the liquid crystal panel 225R.The liquid crystal panel 225R has a function of spatially modulating thered light component LR made incident thereon via the field lens 224R onthe basis of an image signal.

The projector also includes a dichroic mirror 219 along an optical pathof the other color light component separated by the dichroic mirror 217.The dichroic mirror 219 has a function of separating the other colorlight component made incident thereon, for example, into a green lightcomponent LG and a blue light component LB.

The projector also includes a field lens 224G and a liquid crystal panel225G arranged in this order along an optical path of the green lightcomponent LG separated by the dichroic mirror 219. The liquid crystalpanel 225G has a function of spatially modulating the green lightcomponent LG made incident thereon via the field lens 224G on the basisof an image signal.

The projector also includes a relay lens 220, a full-reflection mirror221, a relay lens 222, a full-reflection mirror 223, a field lens 224B,and a liquid crystal panel 225B arranged in this order along an opticalpath of the blue light component LB separated by the dichroic mirror219. The full-reflection mirror 221 reflects the blue light component LBmade incident thereon via the relay lens 220 to the full-reflectionmirror 223. The full-reflection mirror 223 reflects the blue lightcomponent LB, which has been reflected from the full-reflection mirror221 and made incident thereon via the relay lens 222, to the liquidcrystal panel 225B. The liquid crystal panel 225B has a function ofspatially modulating the blue light component LB, which has beenreflected from the full-reflection mirror 223 and made incident thereonvia the field lens 224B, on the basis of an image signal.

The projector also includes, at a position at which the optical paths ofthe red light component LR, the green light component LG, and the bluelight component LB cross each other, a cross-prism 226 having a functionof synthesizing the three color light components LR, LG, and LB. Theprojector also includes a projection lens 227 for projecting thesynthesized light emerged from the cross-prism 226 to a screen 228. Thecross-prism 226 has three incident planes 226R, 226G, and 226B, and oneemergence plane 226T. The red light component LR emergent from theliquid crystal panel 225R is made incident on the incident plane 226R;the green light component LG emergent from the liquid crystal panel 225Gis made incident on the liquid crystal panel 226B; and the blue lightcomponent LB emergent from the liquid crystal panel 225B is madeincident on the incident plane 226B. The cross-prism 226 synthesizes thethree color light components made incident on the incident planes 226R,226G, and 226B, and makes the synthesized light emergent from theemergence plane 226T.

4. Production of Liquid Crystal Display Device

A first embodiment of a method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIGS. 19A to 19E.

FIGS. 19A to 19E are process diagrams showing basic steps of producing aliquid crystal display device according to this embodiment.

FIG. 19A shows a step of bonding a TFT substrate to a base glass. A baseplate such as a base glass 1002 is bonded on a front surface 1001 f of aTFT substrate 1001 via an adhesive 1003 soluble in water or an organicsolvent.

Examples of the adhesives 1003 include a wax such as a hot melt typewater-soluble solid wax or a water-soluble liquid wax, a thermoplasticpolymer adhesive (trade name: Crystal Bond), a cyanoacrylate basedadhesive, and an epoxy based adhesive.

The hot melt type water-soluble solid wax is available from, forexample, Nikka Seiko Co., Ltd. under the trade names of “Aqua Wax20/50/80” (main component: fatty acid glyceride), “Aqua Wax553/531/442/SE” (main component: polyethylene glycol, vinyl pyrrolidonecopolymer, glycerine polyether), and “PEG Wax 20” (main component:polyethylene glycol).

The water-soluble liquid wax is available as a synthetic resin basedliquid adhesive from, for example, Nikka Seiko Co., Ltd. under the tradenames of “Aqua Liquid WA-302 (main component: polyethylene glycol,polyvinyl pyrrolidone derivative, methanol), and WA-20511/QA-20566 (maincomponent: polyethylene glycol, polyvinyl pyrrolidone derivative, IPA(isopropyl alchol), water).

The base glass 1002 may be stuck on the TFT substrate 1001 by means of aUV-cured type adhesive double-coated tape or a thermally-cured typeadhesive double-coated tape.

If needed, to protect the surface of the TFT substrate 1001 or preventcontamination of the surface of the TFT substrate 1001 with halogenions, the front surface 1001 f of the TFT substrate 1001 may be coatedwith a resist film. In addition, the base glass material may be atransparent glass such as borosilicate glass or blue plate glass.

In the case of using the thermoplastic polymer adhesive (trade name:Crystal-Bond) soluble in an organic solvent such as acetone as theadhesive 1003, the bonding step may be performed by coating the baseglass 1002 with the crystal bond dissolved in acetone; overlapping theTFT substrate 1001 to the base glass 1002; heating the TFT substrate1001 and the base glass 1002 overlapped to each other in vacuum under acondition with 150–160° C./13.3322 Pa (0.1 Torr), to remove bubblesinterposed therebetween, thereby bringing the TFT substrate 1001 intoclose-contact with the base glass 1002; and breaking the vacuum, topromote the degassing with the pressure generated upon return toatmospheric pressure and to equalize the thickness of the adhesive 1003,for example, to 1 to 3 μm.

In the case of using the hot melt type water-soluble solid wax (forexample, “Aqua Wax 80/553” or “PEG Wax 20” available from Nikka SeikoCo., Ltd.) as the adhesive 1003, the bonding step may be performed bydissolving 30 to 40 wt % of the wax in methanol and filtering the waxsolution to remove foreign matters; coating the base glass 1002 with thewax solution by spin-coating; overlapping the TFT substrate 1001 to thebase glass 1002; heating the TFT substrate 1001 and the base glass 1002overlapped to each other in vacuum under a condition with 80–100°C./13.3322 Pa (0.1 Torr), to remove bubbles interposed therebetween,thereby bringing the TFT substrate 1001 into close-contact with the baseglass 1002; and breaking the vacuum, to promote the degassing with thepressure generated upon return to atmospheric pressure and to equalizethe thickness of the adhesive 1003, for example, to 1 to 3 μm.

In the case of using the water-soluble liquid wax (for example, “AquaLiquid WA-302” available from Nikka Seiko Co., Ltd.) as the adhesive1003, the bonding step may be performed by coating the base glass 1002with the liquid wax having a viscosity of, for example, 4 to 5 cps byspin-coating; overlapping the TFT substrate 1001 to the base glass 1002;heating the TFT substrate 1001 and the base glass 1002 overlapped toeach other in vacuum under a condition with 70–80° C./13.3322 Pa (0.1Torr), to remove bubbles interposed therebetween, thereby bringing theTFT substrate 1001 into close-contact with the base glass 1002; andbreaking the vacuum, to promote the degassing with the pressuregenerated upon return to atmospheric pressure and to equalize thethickness of the adhesive 1003, for example, to 1 to 3 μm.

In the case of using the double-coated tape as the adhesive 1003, thebonding step may be performed by bonding the base glass 1002 to the TFTsubstrate 1001 by using a polyolefine tape (thickness: 100±2 μm) withits both surfaces coated with an UV-cured type adhesive (thickness: 10±1μm) or a polyolefine tape (thickness: 100±2 μm) with its both surfacescoated with a thermally-cured type adhesive. In this step, vacuumdegassing treatment may be performed to prevent occurrence of bubblestherebetween.

FIG. 19B shows the step of polishing the TFT substrate. In a state thatthe TFT substrate 1001 is held by the base glass 1002, a back surface1001 b of the TFT substrate 1001 is polished to be thinned. For example,the back surface 1001 b of the TFT substrate 1001 is polished by amethod of polishing one surface with a grade suitable for optics whilethe base glass 1002 is taken as a reference plane, to prepare the TFTthin substrate 1001 having a specific thickness (for example, 20±3 μm).As the dimensional accuracy of the base glass 1002, the parallelism isset to 1 to 3 μm and the thickness is 2 mm.

The method for one-surface polishing with a grade suitable for opticsmay be performed by one-surface buffing made in the order of roughbuffing, medium buffing, and finish buffing, wherein particle sizes ofabrasives such as alumina or cerium oxide may be reduced in the order ofthe rough buffing, medium buffing, and finish buffing, to therebygradually increase the polishing accuracy.

The one-surface buffing performed as the method for one-surfacepolishing with a grade suitable for optics may be combined withone-surface blasting. This one-surface blasting involves preparing alaminar flow of high pressure air in which particles of abrasives suchas silicon carbide, boron carbide, or diamond are dispersed, andblasting a specific amount of the laminar flow from a slit-shapedopening at the leading end of a nozzle while scanning the nozzle in thereciprocating directions over the back surface 1001 b of the TFTsubstrate 1001, to polish the back surface 1001 b of the TFT substrate1001. The blasting is followed by finish polishing, that is, finishbuffing, to further increase the polishing accuracy and remove residualstress due to blasting of the particles.

The method for one-surface polishing with a grade suitable for opticsmay be performed by CMP (Chemical Mechanical Polishing). Like theone-surface buffing, the CMP may be performed in the order of roughpolishing, medium polishing, and finish polishing.

The one-surface buffing performed as the method for one-surfacepolishing with a grade suitable for optics may be combined with a methodfor one-surface etching with a grade suitable for glass. This processinvolves reducing the thickness of the TFT substrate 1001 to a specificvalue by the method for etching with a grade for glass, and removingsurface waviness due to the method for etching with a grade suitable forglass by finish buffing performed as the method for polishing with agrade suitable for optics. In this case, it is required to use aprotective adhesive or tape withstanding a hydrofluoric acid basedetchant.

The one-surface CMP performed as the method for one-surface polishingwith a grade suitable for optics may be combined with the method forone-surface etching with a grade suitable for optics. This processinvolves etching the back surface 1001 b of the TFT substrate 1001 madefrom quartz glass to a specific value with a hydrofluoric acid basedetchant, and removing surface waviness due to glass etching by CMPperformed as the method for polishing with a grade suitable for optics.Even in this case, it is required to use a protective adhesive or tapewithstanding a hydrofluoric acid based etchant.

FIG. 19C shows the step of sticking a microlens array on the TFTsubstrate. A microlens array is stuck on the polished back surface 1001b of the TFT substrate 1001 via an optical resin 1005. To be morespecific, this step includes a step of preparing a microlens substrate(ML substrate) 1004 in which microlens planes 1004 r are arranged in atwo-dimensional pattern by processing an optical glass such as quartzglass or crystallized glass (Neo Ceram), and a step of aligning andoverlapping the ML substrate 1004 to the polished back surface 1001 b ofthe TFT substrate 1001, filling a gap therebetween with a transparentoptical resin 1005 having a refractive index higher than that of each ofthe substrates 1001 and 1004, and curing the optical resin 1005. In thiscase, the closed gap is formed between the TFT substrate 1001 and the MLsubstrate 1004 by bonding the ML substrate 1004 to the back surface 1001b of the TFT substrate 1001 via a seal material 1006, and is then filledwith the transparent high refractive index optical resin 1005.

The latter filling/curing step will be more fully described below.

A frame made from the seal material 1006 and having a filling port isformed around the ML substrate (microlens substrate) 1004, and the TFTsubstrate 1001 thinned by polishing is overlapped to the ML substrate1004. In this state, the seal material is cured. If the seal material1006 is composed of a thermally-cured type adhesive, it is curedby-heating at a specific temperature, whereas if the seal material 1006is composed of an UV-cured type adhesive, it is cured by UV-irradiationwith a specific energy. Alternatively, if the seal material 1006 iscomposed of a thermally-cured/UV-cured combination type adhesive, it iscured by combination of heating at a specific temperature andUV-irradiation with a specific energy.

The high refractive index transparent optical resin 1005 is injected inthe gap from the filling port, and the filling port is sealed with aUV-cured type adhesive. The optical resin 1005 is then thermally cured.In the case of using an acrylic based or an acrylic epoxy based highrefractive index transparent resin (viscosity: 20 to 100 cps) as theoptical resin 1005, the filling port is dispense-coated with the resinor dipped in the resin in vacuum, and is injected in the gap through thefilling port with a pressure upon return to atmospheric pressure. Atthis time, a suitable pressure may be added to inject the resin in thegap through the filling port. Such a high refractive index transparentresin is then cured at a temperature of 70 to 80 for 120 min, to obtainthe high refractive index transparent optical resin 1005 having arefractive index of 1.59 to 1.67.

Since the high refractive index optical resin 1005 is injected in thelens planes 1004 r formed in the microlens substrate 1004 having arelatively low refractive index and is cured, the microlenses can beautomatically formed. In addition, to align the lens planes 1004 r onthe microlens substrate 1004 side to pixel electrodes on the TFTsubstrate 1001 side in one-to-one relationship, the TFT substrate andthe ML substrate are overlapped to each other with alignment marksformed on both the TFT substrate and the ML substrate aligned to eachother, and are fixed by the seal material 1006.

FIG. 19D shows the step of peeling the base glass. A spent base glass1002 is peeled from the front surface 1001 f of the TFT substrate 1001,to integrate the microlens array with the back surface 1001 b of the TFTsubstrate 1001. Concretely, the base glass can be peeled from the TFTsubstrate 1001 by heating or UV irradiation. In the case of using athermoplastic polymer (crystal bond) or a cyanoacrylate based adhesiveas the adhesive 1003, after the base glass is peeled by heating, theentire ML substrate is subjected to ultrasonic cleaning using an organicsolvent such as acetone, a combination of acetone and ethanol, methanol,or IPA. In the case of using a hot melt based water-soluble wax (forexample, “Aqua Wax 80/553” or “PEG Wax 20” available from Nikka SeikoCo., Ltd.) as the adhesive 1003, the entire ML substrate is subjected toultrasonic cleaning using pure water or hot pure water at 50 to 60° C.In addition, the spent high accurate base glass is desirable to bere-used after being cleaned.

FIG. 19E shows the step of finishing a liquid crystal display device. Amicrolens TFT substrate (MLTFT substrate) 1007 obtained by integratingthe one-surface polished TFT substrate 1001 with the microlens substrate1004 is overlapped to a microlens counter substrate (ML countersubstrate) 1017 obtained by integrating a microlens substrate with acounter substrate with a specific gap kept therebetween, and the gap isfilled with liquid crystal 1009 and is then sealed, to obtain an activematrix type liquid crystal display device having a dual microlensstructure.

The microlens counter substrate 1017 can be obtained in the same stepsas those for the microlens TFT substrate 1007. To be more specific, thefront surface side of a counter substrate 1011 is polished, and amicrolens substrate 1014 is stuck on the polished surface of the countersubstrate 1011 via a seal material 1016. Microlens planes 1014 r arepreviously formed on the microlens substrate 1014. A gap between thesingle-surface polished counter substrate 1011 and the microlenssubstrate 1014 is filled with a high refractive index transparentoptical resin 1015 and is cured, to obtain the ML counter substrate1017. In addition, a counter electrode is previously formed on the frontsurface, to be brought into contact with the liquid crystal 1009, of thecounter substrate 1011.

The liquid crystal display device produced by the production methodaccording to this embodiment has a panel structure that the liquidcrystal 1009 is held between the pixel electrodes formed on the MLTFTsubstrate 1007 side and the counter electrode formed on the ML countersubstrate 1017 side. The microlens array in which microlensesfunctioning as condenser lenses for respective pixel electrodes arearranged in two-dimensional pattern is integrally formed on the MLcounter substrate 1017 side. The microlens array in which microlensesfunctioning as field lenses for respective pixel electrodes are arrangedin a two-dimensional pattern is integrally formed on the MLTFT substrate1007 side.

In the above-described-polishing step, the TFT substrate 1001 and/or thecounter substrate 1011 are polished to reduce the thicknesses in such amanner that the focal point of each microlens functioning as the fieldlens nearly corresponds to the principal point of the correspondingmicrolens functioning as the condenser lens in the finished panel state.For example, according to this embodiment, since the TFT substrate 1001is thinned to a thickness of about 20 μm, the above requirement can besatisfied. By arranging microlens arrays on both the TFT substrate 1001side and the counter substrate 1011 side such that the focal point ofeach field lens nearly corresponds to the principal point of thecondenser lens, it is possible to enlarge the effective aperture ratioof the pixels at maximum.

Along with the tendency toward finer pixels, the focal point of eachmicrolens tends to become shorter, and correspondingly, it is requiredto reduce the thickness of each substrate to significant degree. Fromthis viewpoint, the production method of the present invention isadvantageous in rationally, efficiently thinning each of the TFTsubstrate and the counter substrate.

The lens planes 1004 r and 1014 r of the microlenses can be each formedinto the spheric, aspheric, or Fresnel plane. The spheric lens isadvantageous in easy production; however, since the radius of curvatureof the lens, which is capable of making the focal distance shortest, islimited to the pixel size, it is difficult to shorten the focal distanceunless the difference in refractive index at the interface between thelens planes can be sufficiently ensured. Each of the aspheric andFresnel lenses is excellent in shortening of the focal distance andplanarity of the lens principal plane, and is very effective to suppressthe divergence angle of light emitted from a light source.

A second embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 20.

FIG. 20 is a process diagram showing the steps of producing the liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in steps S1 to S6 and a single-chip module processis performed in step S7 and S8, with ML counter substrates (single-chipmodule substrates) prepared between steps S7 and S8.

In this embodiment, a large area TFT substrate (TFT large-sizedsubstrate) is used as a multi-chip module substrate for promotingrationalization of the production process. To be more specific, thelarge area substrate (multi-chip module substrate) is used in steps S1to S6, and is divided into single substrates (single-chip modulesubstrates) corresponding to individual panels in step S7.

In step S1, a TFT large-sized substrate having a diameter of, forexample, 8 inches is prepared. In step S2, a base glass having adiameter of 8 inches is stuck on the TFT large-sized substrate. In stepS3, the thickness of the TFT large-sized substrate is reduced to 20 μmby the method for one-surface polishing with a grade suitable foroptics. In step S4, an ML substrate (diameter: 8 inches) in whichmicrolens planes are previously formed is stuck on the polished surfaceof the TFT large-sized substrate by a seal material, and the microlensplanes are filled with a high refractive index resin to form a microlensarray therebetween. In step S5, the spent base glass is peeled and theTFT large-sized substrate is cleaned.

In step S6, the exposed surface of the TFT large-sized substrate issubjected to alignment treatment. For Example, a polyimide alignmentfilm is formed on the surface of the TFT large-sized substrate and issubjected to rubbing treatment. In this case, since the high refractiveindex resin having a relatively low heat resistance is injected to formthe microlens array in the previous step, it may be desirable to use apolyimide alignment film specialized as a type curable at a lowtemperature in the alignment treatment of step S6. However, since manykinds of the recent polyimide resins are curable at relatively lowtemperatures, the polyimide alignment film is not necessarilyspecialized as a type curable at a low temperature. A DLC (diamond likecarbon) film may be used in place of the polyimide alignment film,wherein the DLC film may be subjected to alignment treatment by ionirradiation with specific directivity. Alternatively, a SiOx alignmentfilm formed by obliquely vapor-depositing SiOx may be used in place ofthe polyimide alignment film, wherein alignment of SiOx is obtained byoblique vapor-deposition.

In the case of using a polyimide alignment film, the polyimide film isformed by roll-coating or spin-coating and is subjected to rubbingtreatment by using a buffing material. In the case of using a DLCalignment film, the DLC film having a thickness of about 5 nm is formedand is subjected to alignment treatment by ion irradiation with specificdirectivity. In the case of using a SiO alignment film, the SiO film isformed by obliquely vapor-depositing SiO.

In step S7, the TFT large-sized substrate having the diameter of 8inches is divided into individual single substrates each having a 0.9inch square size, for example, by diving or CO₂ laser cutting. SingleTFT substrates each incorporating a microlens array are thus obtained.

Subsequently, single counter substrates each incorporating a microlensarray, which have been evaluated as non-defective products, areprepared.

In step S8, each of the above single counter substrates is overlapped toone of the single TFT substrates each incorporating a microlens array,which have been evaluated as non-defective products, with a specific gapkept therebetween, and the gap is filled with crystal liquid such asnematic liquid crystal through a filling port, followed by sealing ofthe filling port. To be more specific, a frame of a seal material havinga filling port is formed around a peripheral portion of either themicrolens array incorporating TFT substrate or the microlens arrayincorporating counter substrate. The microlens array incorporating TFTsubstrate is overlapped to-the microlens array incorporating countersubstrate while alignment marks formed on both the substrates arealigned to each other, and the seal material is cured. After the liquidcrystal is injected in the gap through the filling port, the fillingport is sealed with a UV-cured type adhesive. The liquid crystal isheated and rapidly cooled, to adjust alignment of the liquid crystal.

As described above, according to this embodiment, a large areasubstrate, which is to be divided into a plurality of single substratescorresponding to individual panels, is subjected to the bonding step,polishing step, sticking step, and peeling step, to integrate a largearea microlens array corresponding to a plurality of single microlensarrays, and is divided into single substrates corresponding toindividual panels in a suitable step (step S7). Accordingly, it ispossible to promote rationalization of the production process. In thisembodiment, a TFT large-sized substrate, on which a microlens arraycorresponding to a plurality of single microlens arrays is formed, isdivided into single TFT substrates, and each of the single TFTsubstrates is overlapped to one of previously prepared single countersubstrates, on each of which a single microlens array is formed, with aspecific gap kept therebetween, to obtain a panel (step S8). Inaddition, according to this embodiment, after the base glass is peeledfrom the surface of the TFT large-sized substrate and the TFTlarge-sized substrate is cleaned in the peeling step (step S5), analignment layer for alignment of a liquid crystal layer is formed on theexposed surface of the TFT large-sized substrate (see step S6) in atemperature range not to damage the heat resistance of the microlensarray formed in step S4.

FIGS. 21A and 21B are typical diagrams showing a concrete dividingmethod used in the dividing step (step S7) shown in FIG. 20. Thedividing method is performed by dividing a large-sized substrate bydicing or CO₂ laser cutting, to prepare microlens array incorporatingsingle TFT substrates each having a specific size.

As shown in the figures, the method includes two steps. In the firststep (first dicing) shown in FIG. 21A, a large-sized substrate 1007 ispartially diced along boundaries, which are defined to partition alarge-sized substrate 1007 into individual panels, by using a V-cutdicing blade 1021, to form V-shaped grooves in cross-section. In thesecond step (second dicing) shown in FIG. 21B, the grooves of thelarge-sized substrate 1007 are perfectly cut by using a general dicingblade 1022, to separate the large-sized substrate into respectivepanels. With these steps, it is possible to obtain single substrateswith tapered end faces.

By partially dicing the large-sized substrate to form the V-shapedgrooves in the large-sized substrate in the first step and fully dicingthe large-sized substrate to separate the large-sized substrate intosingle substrates in the second step, it is possible to chamfer each ofthe single substrates. The single substrate thus chamfered isadvantageous in preventing occurrence of cracking and chipping of an endface of the TFT thin substrate when the TFT substrate is assembled intothe panel. In addition, each of the first dicing and the second dicingmay be desirable to be continuously performed by using a dual dicer.

A third embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 22.

FIG. 22 is a process diagram showing the steps of producing the liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in steps S1 to S7 and a single-chip module processis performed in step S8, with ML counter substrates (single-chip modulesubstrates) prepared between steps S6 and S7. This embodiment isdifferent from the previous embodiment shown in FIG. 20 in that theabove-described steps S7 and S8 are reversed to each other. In thisembodiment, in step S7, non-defective single ML counter substrateshaving been subjected to alignment treatment are overlapped to anon-defective ML incorporating TFT large-sized substrate having beensubjected to alignment treatment, to be thus assembled, and liquidcrystal is injected in the gap therebetween and is sealed; and in stepS8, the ML incorporating TFT large-sized substrate is divided, to obtainindividual panels. As compared with the previous embodiment shown inFIG. 20, this embodiment is rational because the multi-chip moduleprocess can be continued immediately before the final step. As describedabove, according to this embodiment, after a microlens arraycorresponding to a plurality of single microlens arrays is formed on aTFT large-sized substrate, single counter substrates, on each of which asingle microlens array is previously formed, are assembled to the TFTlarge-sized substrate (step S7), and the TFT large-sized substrate isdivided, to form individual panels (step S8).

FIG. 23 is a typical view showing a concrete assembling method used inthe above-described assembling step S7 shown in FIG. 22. As shown in thefigure, non-defective microlens array incorporating single substrates1017 are overlapped on non-defective portions of the microlensincorporating TFT large-sized substrate 1007 with specific gaps kepttherebetween and are fixed thereto by means of a seal material 1008, andliquid crystal 1009 is injected in gaps between both the substrates 1007and 1017 and is sealed.

To be more specific, after the MLTFT large-sized substrate 10 is coatedwith the seal material 1008 of a UV-cured or thermally-cured type, theML counter substrates 1017 are positioned to corresponding portions ofthe MLTFT large-sized substrate 1007 by using alignment marks providedtherefore and are overlapped thereto with a specific gaps kepttherebetween, and are fixed thereto by curing the seal material 1008 byUV irradiation or heating. The liquid crystal is then injected in thegaps through filling ports, and the filling ports are sealed by aUV-cured type adhesive.

After the assembling work in step S7 is thus completed, the MLTFTlarge-sized substrate 1007 is divided into single substrates by dicingor laser cutting. As shown by a dashed line, the MLTFT large-sizedsubstrate 1007 is diced along boundaries of respective panels, to obtainpanels. At this time, to prevent occurrence of cracking or chipping ofan end face of the TFT thin substrate 1007, the dicing is preferablyperformed such that the TFT thin substrate 1007 is partially diced alongthe boundaries by using a V-cut dicing blade, to form V-shaped grooves,and the grooves of the TFT thin substrate 1007 are perfectly cut byusing a general dicing blade, to separate the TFT thin substrate intorespective panels.

FIGS. 24A and 24B are process diagrams showing one example of the methodof producing the ML counter substrate 1017 shown in FIG. 23.

As shown in FIG. 24A, a frame of a seal material 1016 is formed around aperipheral portion of an ML substrate 1014 on which microlens planes1014 r are previously formed. A cover glass substrate 1011 is overlappedto the ML substrate 1014 with a specific gap kept therebetween. In sucha state, the seal material 1016 is cured.

As shown in FIG. 24B, a high refractive index transparent optical resin1015 is injected in a gap between the cover glass substrate 1011 and theML substrate 1014 and is cured by heating, and the gap is sealed by aUV-cured type adhesive. The thickness of the back surface side of thecover glass substrate 1011 is reduced by the method for one-surfacepolishing with a grade suitable for optics, to prepare the ML countersubstrate 1017. A transparent conductive film such as ITO is formed overthe polished back surface of the cover glass substrate 1011, to form acounter electrode 1018. A polyimide alignment film 1019 is formed on thecounter electrode 1018, and is subjected to alignment treatment such asrubbing treatment. At this time, the thickness of the ML countersubstrate 1017 may be adjusted to a specific value by polishing the MLsubstrate 1014 and the cover glass substrate 1011 in accordance with amethod for both-surface polishing with a grade for optics. In this case,after the ML substrate 1014 is formed by filling the microlens planes1014 r with a high refractive index transparent resin, a transparentresin film may be formed on the surface, opposed to the microlensplanes, of the resin and further a SiO₂ film be formed thereon bysputtering or vapor-deposition. The formation of such a stacked layerfilm can eliminate the need of provision of the cover glass substrate1014, to reduce the production cost.

The single ML counter substrates 1017 thus formed are assembled on themulti-chip module type large-sized MLTFT substrate 1007 shown in FIG.23.

A fourth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 25.

FIG. 25 shows the steps of producing a liquid crystal display device inthis embodiment, wherein a multi-chip module process is performed insteps S1 to S6 and a single-chip module process is performed in steps S7and S8, with ML counter substrates (single-chip module substrates)prepared between steps S7 and S8.

This embodiment is modified from the embodiment shown in FIG. 20.

In the embodiment shown in FIG. 20, the microlens array made from a highrefractive index resin is formed between the TFT large-sized substrateand the ML large-sized substrate in step S4, and a polyimide alignmentfilm is formed on the TFT large-sized substrate and is subjected toalignment treatment in step S6. In these steps, depending on the heatresistance of the high refractive index resin used for the microlensarray, the polyimide film used for alignment treatment must be selectedas a low temperature curable polyimide film.

On the contrary, in this embodiment, a polyimide film for alignmenttreatment is first formed in step S2, and then a microlens array madefrom a high refractive index resin is formed in step S5. The polyimidefilm for alignment treatment is thus not required to be selected as alow temperature curable polyimide film, but may be selected as a hightemperature curable polyimide film excellent in performance andstability.

In this way, according to this embodiment, before a series of steps,that is, a bonding step, a polishing step, a sticking step, and apeeling step are performed to integrate a microlens array to the backsurface of a TFT large-sized substrate, an alignment step for forming analignment layer used for alignment of a liquid crystal layer on thesurface of the TFT large-sized substrate is performed (step S2).

A general polyimide resin is curable at a high temperature of about 180°C., whereas a general high refractive index transparent resin is curablea low temperature ranging from 60 to 120° C. Accordingly, it isundesirable to form a film made from a general polyimide on the TFTlarge-sized substrate on which a microlens array made from a generalhigh refractive index transparent resin has been mounted. For thisreason, in the embodiment shown in FIG. 20, a low temperature curablepolyimide film or a DLC film is used as an alignment film. On thecontrary, in this embodiment, since an alignment film for alignmenttreatment is formed before a microlens array made from a high refractiveindex resin is formed, a film made from a general polyimide resincurable at a high temperature of about 180° C. can be used as thealignment film.

A fifth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 26.

FIG. 26 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in steps S1 to S6 and a single-chip module processis performed in steps S7 and S8, with ML counter substrates (single-chipmodule substrates) prepared between steps S6 and S7.

In this embodiment, like the previous embodiment shown in FIG. 22,single ML counter substrates are assembled to a MLTFT large-sizedsubstrate and then the MLTFT large-sized substrate is divided intosingle substrates corresponding to individual panels; however, unlikethe previous embodiment shown in FIG. 22, the alignment treatment usingan alignment film is performed in step S2, and then the formation of amicrolens array using a high refractive index transparent resin isperformed in step S5. As a result, like the embodiment shown in FIG. 25,a film made from a high temperature curable polyimide resin can be usedas the alignment film.

A sixth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 27.

FIG. 27 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in steps S1 to S7 and a single-chip module processis performed in step S8, with an ML counter large-sized substrate(multi-chip module substrate) prepared between steps S6 and S7.

According to this embodiment, in step S7, an ML counter large-sizedsubstrate is assembled to an MLTFT large-sized substrate, and in stepS8, the assembly of the MLTFT large-sized substrate and the ML counterlarge-sized substrate is divided into individual panels. Since both thelarge-sized substrates are used immediately before the final step, theproduction process is more rationalized. In this embodiment, however,the selection of whether products are non-defective or defective isperformed by inspection for single products after the final step.

As described above, according to this embodiment, the ML counterlarge-sized substrate incorporating a microlens array corresponding to aplurality of single microlens arrays is overlapped to the MLTFTlarge-sized substrate incorporating a microlens array corresponding to aplurality of single microlens arrays with a specific gap kepttherebetween, to be assembled into a large-sized panel portioncorresponding to a plurality of panels (step S7), and the assembly isdivided into individual panels (step S8). In addition, according to thisembodiment, the microlens array using a high refractive indextransparent optical resin is formed in step S4, and a low temperaturecurable polyimide film or a DLC film for alignment treatment is formedin step S6.

A seventh embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 28.

FIG. 28 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in steps S1 to S7 and a single-chip module processis performed in step S8, with an ML counter large-sized substrate(multi-chip module substrate) prepared between steps S6 and S8.

In this embodiment, like the previous embodiment shown in FIG. 27, an MLcounter large-sized substrate is assembled to a TFT large-sizedsubstrate, and then the assembly is divided into individual panels;however, unlike the previous embodiment shown in FIG. 27, an alignmentfilm for alignment treatment is formed in step S2 and a microlens arrayusing a high refractive index transparent optical resin is formed instep S5. Accordingly, a general high temperature curable polyimide filmcan be used as the alignment film for alignment treatment.

An eighth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 29.

FIG. 29 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment, wherein a multi-chip processis performed in step S1 and a single-chip module process is performed insteps S2 to S8, with ML counter substrates (single-chip modulesubstrates) prepared between steps S7 and S8.

In this embodiment, unlike the previous embodiments, panels are obtainedby basically adopting a single-chip module process in place of amulti-chip module process.

A TFT large-sized substrate having a diameter of 8 inches is prepared instep S1, and is then divided into TFT single substrates each having a0.9 inch square size by dicing or CO₂ laser cutting. If needed, the TFTsingle substrate may be coated with a resist film for protecting thesurface and preventing contamination due to a halogen gas.

In step S3, a base glass having a 0.9 inch square size is stuck on eachof the TFT single substrates. The base glass may be borosilicate glassand the TFT substrate may be made from synthetic quartz glass. Theparallelism of the base glass is accurately finished to 1 to 2 μm. Thebase glass is bonded to the TFT substrate by means of a double-coatedtape of a thermoplastic transparent polymer type or UV-cured typeadhesive or a double-coated tape of a thermosetting type adhesive.

In step S4, the back surface of the TFT substrate is polished by themethod for one-surface polishing with a grade suitable for optics to bethinned to a thickness of 20 μm. A variation in thickness of the TFTsubstrate is preferably suppressed within ±3 μm. In step S5, a microlenssubstrate (ML substrate) having a 0.9 inch square size, in whichmicrolens planes are previously formed, is overlapped to the thinned TFTsubstrate, and a high refractive index transparent resin is injected ina gap therebetween and is sealed.

In step S6, the base glass is peeled from the TFT substrate by, forexample, heating, and the TFT substrate is cleaned with an organicsolvent. The peeled base glass, which is highly accurately finished, isre-usable. In addition, the base glass may be peeled and the TFTsubstrate may be cleaned after curing of a seal material by UVirradiation in the subsequent step. In step S7, alignment treatment isperformed by, for example, forming a low temperature curable polyimidealignment film and subjecting the polyimide film to rubbing treatment abuffing material; or forming a DLC film and subjecting the DLC film toion irradiation with directivity.

In step S8, a single ML counter substrate is overlapped to the MLTFTsubstrate with a specific gap kept therebetween, and liquid crystal isinjected in the gap and is sealed. To be more specific, a frame of, forexample, a UV-cured type seal material is formed on one of thesubstrates, and the other substrate is overlapped thereto with aspecific gap kept therebetween while alignment marks provided thereforeare aligned to each other. The seal material is cured by UV irradiation,to fix both the substrates to each other. An empty panel (in the statebefore being filled with liquid crystal) is thus obtained. Liquidcrystal is injected in the panel via a filling port formed in the sealmaterial and is sealed, to finish a duel microlens array type liquidcrystal display device.

A ninth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 30.

FIG. 30 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment, wherein a multi-chip moduleprocess is performed in step S1 and a single-chip module process isperformed in steps S2 to S8, with ML counter substrates (single-chipmodule substrates) prepared between steps S7 and S8.

In this embodiment, like the previous embodiment shown in FIG. 29,panels are obtained by basically adopting a single-chip module process;however, unlike the previous embodiment shown in FIG. 29, an alignmentfilm for alignment treatment is formed in step S3, and a microlens arrayusing a high refractive index transparent optical resin is formed afterthe ML substrate is stuck on the TFT substrate in step S6.

A tenth embodiment of the method of producing a liquid crystal displaydevice according to the present invention will be described withreference to FIG. 31.

FIG. 31 is a process diagram showing the steps of producing a liquidcrystal display device in this embodiment.

In a preliminary step, an ML counter substrate 1017 obtained byintegrating a microlens array to a first substrate on which a counterelectrode is previously formed is prepared. In an assembling step, thecounter substrate (ML substrate) 1017 integrated with the microlensarray is overlapped to the front surface 1001 f of a TFT substrate 1001on which pixel electrodes and switching devices for driving the pixelelectrodes are previously formed with a specific gap kept therebetween,and liquid crystal is injected in the gap and sealed, to obtain a panel.In a bonding step, a base glass 1002 is bonded to the ML countersubstrate 1017 overlapped to the front surface 1001 f of the TFTsubstrate 1001 by using an adhesive 1003 such as a hot melt basedwater-soluble wax, bees wax, or a cyanoacrylate based adhesive. Theadhesive 1003 may be that obtained by diluting an acrylate with anon-chlorine based organic solvent (acetone, a combination of acetoneand ethanol, or IPA). In a polishing step, in the state being held bythe base glass 1002, the back surface 1001 b of the TFT substrate ispolished. In a sticking step, a microlens array is stuck on the polishedback surface 1001 b of the TFT substrate 1001.

Unlike the previous embodiments, after a panel is previously prepared,the back surface of the TFT substrate is polished and the microlensarray is stuck on the polished back surface of the TFT substrate.

In the production method shown in FIG. 31, since the TFT substrate 1001on which pixel electrodes and thin film transistors are previouslyintegrated is polished, it is desirable to take a measure againstdamages due to static electricity.

FIG. 32 shows an example of the measure against damages due to staticelectricity, wherein a conductive paste 1024 with no residual coatingportion is used as the measure against damages due to staticelectricity. As shown in FIG. 32, a tape, particularly, a conductivepaste tape with no residual coating portion having a thickness nearlyequal to that of the microlens incorporating counter substrate 1017 isprovided in such a manner as to be short-circuited with an outputterminal formed on the TFT substrate 1001, wherein the base glass isfixed to the ML counter substrate 1017 with an adhesive 1003.

FIG. 33 shows another example of the measure against damages due tostatic electricity. As shown in FIG. 33, a connector 1026 composed of aflexible printed board for external connection is mounted to aconnection terminal of the TFT substrate 1001 by thermo-compressionbonding, and the base glass 1002 is fixed to the ML counter substrate1017 by the adhesive 1003 or a double-coated tape. To stabilize theconnector 1026, a gap between the base glass 1002 and the TFT substrate1001 is filled with the adhesive 1003 or filled with a tape member 1025having a thickness nearly equal to that of the microlens arrayincorporating counter substrate 1017. The connector 1026 may be shortento an extent not to exert adverse effect on polishing of the TFTsubstrate 1001 by the method for one-surface polishing with a gradesuitable for optics in the subsequent step, and the terminal of theconnector 1026 is short-circuited or covered in order not to becontaminated by abrasive or the like. In this way, to take the measureagainst damages due to static electricity, the back surface of the TFTsubstrate 1001 is polished in the state that a plurality of terminalsfor external connection formed on the TFT substrate are kept at the samepotential.

FIG. 34 is a typical diagram showing the polishing treatment for thepanel shown in FIG. 32. As shown in the figure, the base glass 1002 sideof the panel is stuck on a work holder 1029 for polishing, and the backsurface 1001 b of the TFT substrate 1001 is polished with the base glass1002 taken as a reference. To prevent the liquid crystal 1009 enclosedin the panel from being heated to a transition temperature or more, itis desirable to cool the TFT substrate 1001 during polishing thereof bythe method for one-surface polishing with a grade suitable for optics.This makes it possible to keep the alignment state of the liquid crystal1009. In the example shown in the figure, one-surface buffing isperformed as the method for one-surface polishing with a grade suitablefor optics. The back surface 1001 b of the TFT substrate 1001 is pressedto a polishing platen 1027 by applying a specific load to the TFTsubstrate 1001. At this time, a specific amount of abrasive is suppliedto the polishing platen 1027.

To be more specific, the polishing work is performed by rotating thepolishing platen 1027 such as a tin platen, a vinyl platen, or clothplaten on its axis, constantly dropping a specific amount of a liquidsuch as water, oil, or organic solvent containing abrasive such assilicon carbide, alumina, or diamond on the polishing platen 1027,pressing a workpiece fixed to the work holder 1029 to the polishingplaten 1027 with a specific load applied to the workpiece, and polishingthe surface of the workpiece. The polishing is made in the order ofrough polishing, medium polishing, and finish polishing, and theparticle size of the abrasive is correspondingly reduced to graduallyincrease the polishing accuracy. If the amount to be polished is large,the workpiece is thinned to a thickness close to a target thickness byrough-polishing, and is then finished by medium-polishing andfinish-polishing. If the TFT substrate 1001 has a thickness of 800 μm,the substrate 100 is thinned to a thickness of 100 μm by rough-polishingand further thinned to a thickness of 50 μm by medium-polishing, and isfinished to a thickness of 20 μm by finish-polishing. In this case,assuming that the allowance of the thickness of the TFT substrate is20±3 μm, finish polishing is performed while the residual thickness ischecked by an optical or laser type step depth meter with the alignmentmark on the surface of the TFT substrate taken as a reference for eachpolished amount of 10 μm. During such polishing, the panel is notpeeled. This is because the TFT substrate is overlapped to the countersubstrate with a gap of 1 to 3 μm kept therebetween and is fixed theretoby the seal material, and further the spacer is in contact with everypixel.

FIG. 35 is a typical diagram showing a polishing treatment usingblasting of particles. As shown in the figure, the blasting is performedby preparing a laminar flow of high pressure air in which particles ofabrasives such as silicon carbide, boron carbide, or diamond aredispersed, and blasting a specific amount of the laminar flow from aninjection port at the leading end of a slit-shaped nozzle 1030 whilescanning the nozzle in the reciprocating directions over the backsurface 1001 b of the TFT substrate 1001, to polish the back surface1001 b of the TFT substrate 1001. The blasting is made in the order ofrough blasting, medium blasting, and finish blasting, and the particlesize of the abrasive is correspondingly reduced to gradually increasethe polishing accuracy. If the amount to be polished is large, theworkpiece is thinned to a thickness close to a target thickness byrough-blasting, and is then finished by medium-blasting andfinish-blasting. If the TFT substrate 1001 has a thickness of 800 μm,the substrate 100 is thinned to a thickness of 300 μm by rough-blastingand further thinned to a thickness of 200 μm by medium-blasting, and isfinished to a thickness of 50 μm by finish-blasting.

Assuming that the allowance of the thickness of the TFT substrate is20±3 μm, after the TFT substrate is finished to a thickness of 50 μm byfinish-blasting, the TFT substrate may be further finished byfinish-buffing performed as the method for polishing with a gradesuitable for optics shown in FIG. 34. The finish polishing is performedwhile the residual thickness is checked by an optical or laser type stepdepth meter with the alignment mark on the surface of the TFT substratetaken as a reference for each polished amount of 10 μm.

FIG. 36 shows a step of sticking the ML substrate 1004 to the backsurface of the TFT substrate 1001 after the polishing step shown in FIG.34. As shown in the figure, in the state that the base glass 1002, theML incorporating counter substrate 1017, and the TFT substrate 1001 areintegrated with each other, a frame of a seal material 1006 made from aUV-cured type adhesive or a UV-cured/thermal-cured combination typeadhesive is formed around a peripheral portion of the back surface ofthe TFT thin substrate 1001 by dispense-coating of the seal material1006. The ML substrate 1004 is overlapped to the TFT thin substrate 1001with a specific gap kept therebetween while alignment marks providedtherefore are aligned to each other, and the seal material 1006 is curedby UV irradiation. At this time, the focal distance of each microlens isfinely adjusted by the thickness of the seal material 1006. For easyfine adjustment, the seal material 1006 may contain a spacer havingspecific sizes in an amount not to degrade the seal characteristic. Thespace is made from a metal, glass, ceramic, or the like. These materialsmay be used singly or in combination. The material is preferably used inthe form of particles having spherical shapes or fiber shapes.

FIG. 37 shows a filling step after the sticking step shown in FIG. 36.As shown in the figure, a high refractive index transparent opticalresin 1005 is press-injected under vacuum in the gap through a fillingport provided in the frame-shaped seal material 1006 and the fillingport is sealed with a UV-cured type adhesive. While not shown, in thecase of using a cyanoacrylate based adhesive as the adhesive 1003, thecyanoacrylate based adhesive is melted by heating, to peel the baseglass 1002, followed by cleaning of the entire panel with an organicsolvent such as IPA, acetone, a combination of acetone and ethanol, ormethanol. In the case of a hot melt type water-soluble wax as theadhesive 1003, the water-soluble wax is melted by heating, to peel thebase glass-1002, followed by ultrasonic cleaning of the entire panelwith pure water or hot pure water at 50 to 60° C.

FIG. 36A shows an example that a jig 1002 a is used in place of a baseglass for supporting the panel. The jig 1002 a serving as a base glassis fixed to a work holder 1029 of a polishing platen. Passages 1002 bfor vacuum attraction are formed in the jig 1002 a and the work holder1029. The panel obtained by assembling the TFT substrate 1001 to themicrolens array incorporating counter substrate 1017 is polished in astate being fixed by the jig 1002 a. In this case, to prevent damagesdue to static electricity upon polishing, it is desirable toshort-circuit an external connection terminal 1001 t of the TFTsubstrate 1001 to a conductive pad 1002 p provided on the jig 1002 a.

FIGS. 38B and 38C show an example that LCD panels are fixed to a workholder 1029 of a large-sized polishing platen provided with a pluralityof jigs 1002 a serving as base glasses. The ML counter substrate 1017side of each panel is set in a recess of the jig 1002 a with the TFTsubstrate 1001 side directed upwardly and is fixed thereto by vacuumattraction, and in such a state, the back surface of the TFT substrateis polished. Even in this case, to prevent damages due to staticelectricity upon polishing, it is desirable to short-circuit an externalconnection terminal of the TFT substrate to a conductive pad provided onthe jig 1002 a.

In general, the synthetic quartz glass as a material of a TFT substrateand a counter substrate for a high temperature polysilicon TFTLCD usedfor a projector is specified to be finished with high accuracy in termsof surface roughness and dimensions. From this viewpoint, according tothe embodiments shown in FIGS. 31 to 38, the counter substrate can beused in place of the base glass by sufficiently checking the filmthickness of the counter substrate during polishing, to eliminate theneed of provision of the base glass, thereby reducing the productioncost.

FIG. 39 is a typical sectional view showing a further example of aliquid crystal display device produced according to the presentinvention.

A microlens array incorporating counter substrate 1017 is overlapped toa microlens array incorporating TFT substrate 1007 with a specific gapkept therebetween and is fixed thereto, and liquid crystal 1009 isenclosed in a gap therebetween. Here, a microlens array integrated onthe back surface of the TFT substrate 1001 thinned by polishing isconfigured such that lens planes “r” have a double structure. To be morespecific, convex lens planes “r” formed on a transparent resin layer1004 having a refractive index “ng1-2” are oppositely spaced from convexlens planes “r” formed on a transparent resin layer 1004′ having arefractive index “ng2-2” by means of a seal material 1006, and atransparent optical resin 1005 having a refractive index “n1” isenclosed therebetween, to form the microlens array. At this time, therefractive index “n1” of the transparent optical resin 1005 is lowerthan each of the refractive index “ng1-2” of the transparent resin layer1004 and the refractive index “ng2-2” of the transparent resin layer1004′. The microlens array incorporating counter substrate 1017 side hasthe same configuration, wherein a transparent optical resin 1015 havinga refractive index “n1” is inserted between a transparent resin layerhaving a refractive index “ng1-1” and a transparent resin layer having arefractive index “ng2-1”.

FIG. 40 shows an example showing the concrete shape and size of a liquidcrystal display device produced according to the present invention. AnMLTFT substrate 1007 is overlapped to an ML counter substrate 1017 witha specific gap kept therebetween and is fixed thereto, and liquidcrystal 1009 is enclosed in a gap therebetween. The focal distance(equivalent value in air) of each microlens on the ML counter substrate1017 side is F1=30.69 μm. The microlens has a structure that atransparent resin layer having a refractive index of 1.45 is in contactwith a transparent optical resin 1015 having a refractive index of 1.66at a boundary defined by a lens plane 1014 r. A counter substrate 1011is made from the crystallized glass “Neo Ceram” and is thinned bypolishing. The depth of the lens plane 1014 r is 10.3 μm and the countersubstrate 1011 is thinned to 20 μm. On the other hand, the focaldistance (equivalent value in air) of each microlens formed on the MLTFTsubstrate 1007 is F2=41.4 μm (actual distance: 64.6 μm). A transparentresin layer having a refractive index of 1.44 is in contact with atransparent optical resin 1005 having a refractive index 1.596 at aboundary defined by the lens plane 1004 r, to form the microlens. Aquartz glass 1001 having a refractive index of 1.46 is thinned to 20 μm.As a result, the distance between principal points of the microlensfunctioning as a condenser lens formed on the ML counter substrate 1017side and the microlens functioning as a field lens formed on the MLTFTsubstrate 1007 side is 64.6 μm. In addition, a TFT pixel pitch is 18 μm.The above dimensions are all actual dimensions except for the focaldistances.

As described above, an effect of the present invention is to eliminatethe need of provision of a cover glass, which has been required for amicrolens array such as a single microlens array (SML) or a duelmicrolens array (DML), and hence to contribute to thinning of amicrolens array. Another effect is that since a microlens array having aplanarized surface is mounted in a liquid crystal panel, the mechanismstress applied to the microlens array can be reduced. Accordingly, thepresent invention is advantageous in producing a microlens array with ahigh efficiency and a high accuracy, and in improving the yield and theperformance of the microlens array.

A further effect of the present invention is to realize a liquid crystaldisplay device having a duel microlens array configuration that onemicrolens array is disposed on a counter substrate side and the othermicrolens array is disposed on a TFT substrate side. Such a displaydevice is advantageous in improving an effective aperture ratio and theutilization efficiency of light emitted from a light source, therebyenhancing the luminance. A projector, to which the liquid crystaldisplay device according to the present invention is applied, makes itpossible to realize the downsizing of the projector and thecost-reduction of a projection lens.

Since a TFT large-sized substrate is divided by partially dicing the TFTlarge-sized substrate so as to form V-shaped grooves and fully dicingthe large-sized substrate at the V-grooves, it is possible to chamferthe single substrates. The single substrate thus chamfered isadvantageous in preventing occurrence of cracking and chipping of theTFT thin, thereby improving the yield and quality. Additionally,according to the present invention, it is possible to prevent damagesdue to static electricity and cracking of a TFT thin substrate uponpolishing of the TFT thin substrate by a method for one-surfacepolishing with a grade suitable for optics, and hence to improve theyield and quality.

While the preferred embodiments of the present invention have beendescribed using the specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the followingclaims

1. A method of producing a microlens array, comprising: a patterningstep of forming a first optical resin layer having a first refractiveindex on a transparent substrate and forming a plurality of microlensplanes arrayed in a two-dimensional pattern on the front surface of saidfirst optical resin layer; a filling step of filling irregularities ofthe microlens planes with a resin having a second refractive index; anda planarizing step of planarizing the front surface, opposed to themicrolens planes, of said resin filling the microlens planes, to form asecond optical resin layer; wherein said planarizing step is performedby planarizing the front surface of said resin filling the microlensplanes by a flat stamping process wherein the first optical resin layeris made from a UV-cure type resin having a low refractive index.